Glossary of Terms

Explore essential terms and concepts in freshwater aquariums with this glossary. Clear, easy-to-understand definitions to help you navigate the hobby effectively.


Aeration: The process of adding oxygen to the water in an aquarium; often achieved through the use of an air pump and an air stone.

Aerobe: Organisms that live in environments where oxygen is present and require it to survive; in contrast to anaerobes.

Air Check Valve: A device placed between the air pump and the aquarium to prevent water from flowing back into the air pump, often used as a safety measure.

Air Driven: Filters or devices that utilize compressed air to function; often quieter and less energy-intensive than electrically driven units.

Air Pump: A small external device that pumps air into an aquarium through a tube; used to improve water oxygenation.

Air Stone: A porous piece of material connected to an air pump to diffuse the air into the aquarium, often making the bubbles smaller and less noisy.

Airline: A tube that transports air from an air pump to an air stone or other air-driven device in an aquarium.

Alder Cone: The seed cones from alder trees; often used in aquariums for their tannins and as a food source for some invertebrates.

Algae: Simple aquatic plants that can grow on various surfaces; often viewed as pests but some types are beneficial.

Algae Scraper: A tool designed to remove algae from the inside walls of an aquarium; usually made of plastic or metal.

Algicide: Chemical agents specifically designed to kill or control the growth of algae in an aquarium.

Algae Wafer: A type of fish food designed to sink to the bottom of the aquarium; commonly used to feed herbivorous bottom dwellers.

Alkaline: Water or solutions with a pH level greater than 7; opposite of acidic.

Alkalinity: The water’s capacity to resist changes in pH; closely related to hardness and buffering capacity.

Alkalinity Test: A specific test used to measure the buffering capacity of water; often a part of standard aquarium water testing kits.

Ammonia (NH3): A toxic waste product produced from fish waste and decaying organic matter; harmful to fish and needs to be monitored.

Ammonia Burn: A condition that occurs when fish are exposed to high levels of ammonia; often results in red or inflamed gills.

Ammonia Test: A diagnostic test commonly used to measure the levels of ammonia in aquarium water; often used in routine water quality monitoring.

Anaerobe: Organisms that can live without oxygen; often found in deep substrate or other areas where oxygen is scarce.

Anaerobic: Environments where oxygen is not present or available; often found in the deeper layers of substrate.

Anal Fin: A fin located on the underside of fish, between the pelvic fins and the tail; helps with stabilization during swimming.

Anoxic: Conditions where there is an absence of free oxygen but might have bound forms of oxygen; often occurs in deep water or substrate layers.

Anti-chlorine: A chemical substance used to neutralize chlorine in tap water; essential when using tap water in an aquarium.

API Test Kits: Commercial water testing kits produced by Aquarium Pharmaceuticals Inc.; commonly used to test various water parameters like pH, ammonia, nitrites, and nitrates.

Aquascape: The arrangement and design of rocks, plants, and substrates in an aquarium; aims for aesthetically pleasing setups.

Aquarium Stand: A specialized piece of furniture designed to support the weight of a full aquarium; available in various materials and designs.

Aragonite: A type of calcium carbonate used as a substrate; popular in aquariums that house hard water fish species.

Asexual Reproduction: A type of reproduction where an organism produces offspring without mating; common in some plants and microorganisms.

Aufwuchs: A layer of algae, detritus, and microorganisms that forms on submerged surfaces; serves as a food source for some fish and invertebrates.

Auto Feeder: An automatic device that dispenses fish food at scheduled times; useful for maintaining a consistent feeding schedule.

Autotrophic: Organisms capable of synthesizing their own food, typically via photosynthesis; includes some algae and plants.


Background: This is a decorative layer you can attach to the back of your aquarium. It’s often made from materials like plastic, paint, or vinyl, and helps to make the tank’s interior pop visually.

Barbells: These are like little whiskers near the mouths of some types of catfish. They’re not just for show; they have taste buds and are important for sensing the environment.

Bare Bottom: This is an aquarium without any gravel, sand, or plant life on the bottom. It’s easier to clean and is often used for quarantine or hospital tanks.

Beef Heart: This is the heart muscle of a cow, finely chopped up. It’s mainly used as a high-protein food for certain types of carnivorous fish, such as cichlids.

Beneficial Bacteria: These are the good bacteria that help break down waste in your tank. They’re crucial for a process called the nitrogen cycle, which helps keep your tank’s environment healthy.

Bio Balls: These are small, plastic balls designed to be housed in your filter. Their design maximizes surface area, allowing beneficial bacteria to thrive and better clean your tank’s water.

Bioload: This term refers to the total amount of waste that living organisms produce in a tank. Too much bioload can strain your filtration system.

Biological Filtration: This is a natural way to clean your tank’s water. Beneficial bacteria break down harmful waste products, turning them into less harmful substances.

Biological Load: This encompasses the entire living weight in your aquarium, from fish to plants to microscopic bacteria.

Biomedia: These are specialized materials that go into your filter to provide more surface area for beneficial bacteria, helping to improve water quality.

Biotope Aquarium: This type of aquarium mimics a specific natural environment. Every element, from the fish to the plants to the water chemistry, aims to replicate a specific habitat in the wild.

Black Beard Algae (BBA): This is a type of algae that appears as dark, fuzzy patches on plants and other surfaces in the tank. It can be challenging to remove.

Blackwater Environments: These are dark, tannin-rich aquatic environments often found in slow-moving rivers that run through forests.

Bladder: In some fish, this internal organ helps with buoyancy, enabling the fish to easily swim at different depths.

Bloom: This refers to a rapid increase in algae or bacteria in your tank, often making the water cloudy.

Bottom Feeder: These are creatures that scavenge for food on the bottom of the tank. They often eat leftover food, algae, and waste.

Brackish: This describes water that has more salt than typical freshwater but less than full saltwater, often found in estuaries where rivers meet the sea.

Breather Bag: These are special bags used for fish transportation. They allow oxygen in and let carbon dioxide out, improving conditions for the fish inside.

Break-in Cycle: This is the initial period when a new tank is getting its biological filtration up and running. It’s an essential part of setting up a new aquarium.

Buffering Capacity: This is the water’s ability to resist changes in pH. A higher buffering capacity means a more stable pH level.

Buffers: These are chemicals that you can add to your tank’s water to help maintain a stable pH level.


Calcification: This refers to the buildup of calcium salts, often in the tissues or shells of aquatic creatures like snails and crustaceans.

Calcium (Ca): This is a chemical element commonly found in water. It’s particularly important for the health and growth of creatures with shells, like snails and some crustaceans.

Calcium Carbonate (CaCO3): This is a specific chemical compound made up of calcium, carbon, and oxygen. It’s often a major component in the shells of aquatic creatures.

Canister Filter: This is a type of external filter that sits outside of your tank. It sucks water out of the tank, cleans it, and then pumps it back in.

Captive-Bred: These are animals that were born and raised in captivity, rather than being caught in the wild.

Carbonate Hardness (KH): This is a measure of how much carbonate and bicarbonate is in the water, which can affect the water’s buffering capacity.

Carnivore: This is any animal that mainly eats meat. In an aquarium, carnivorous fish might eat smaller fish, specialized pellets, or meaty foods like shrimp.

Caudal Fin: This is the fin at the very back end of a fish—the one that looks like a tail. It’s primary role is to help the fish move forward.

Ceramic Biomedia: These are pieces of unglazed ceramic that live in your filter. Their porous structure provides a lot of surface area for beneficial bacteria to live on.

Chemical Filtration: This involves using special chemical substances to remove unwanted chemicals from your tank’s water.

Chiller: This is a device that cools down your aquarium’s water. It’s like a mini air conditioner for your tank, often used in setups that require a lower, stable temperature.

Chloramine (CH2Cl): This is a chemical made of chlorine and ammonia. Some cities add it to the tap water to kill bacteria.

Chlorine (Cl): This chemical is commonly added to tap water to kill bacteria. It’s harmful to fish and needs to be removed before adding tap water to an aquarium.

Circulation: This is the constant movement of water in your aquarium, achieved through filters and pumps. Good circulation is crucial for oxygen distribution and waste removal.

Clarifier: This is either a device or a chemical that helps to clear up cloudy water by clumping tiny particles together.

CO2 (Carbon Dioxide): This is a gas that fish exhale and plants take in. In planted tanks, extra CO2 is often added to help the plants grow better.

CO2 Diffuser: This is a special device that takes larger bubbles of CO2 gas and breaks them down into much smaller bubbles, making it easier for plants to absorb.

CO2 Injection: This involves using a pressurized system to add CO2 to your tank. It’s often used in planted tanks to help the plants grow more robustly.

Conditioner: This is a chemical treatment for tap water that neutralizes harmful substances like chlorine.

Community Fish: These are typically small, peaceful fish that get along well with other species. They are ideal for community tanks where multiple species coexist.

Community Tank: This is an aquarium that houses multiple species of fish that are known to live peacefully with each other.

Corner Filter: This is a small, often air-powered filter that fits into the corner of your tank. It’s good for small tanks or as a backup filtration system.

Crustacean: This is a type of invertebrate animal that has a hard outer shell. Think of creatures like shrimp, crabs, and lobsters.

Cyanobacteria: Also known as blue-green algae, these are photosynthetic bacteria that can form slimy mats on your aquarium surfaces.

Cycling: This is the process of establishing a stable population of beneficial bacteria in your aquarium. It’s essential for breaking down waste and keeping your fish healthy.


Daphnia: These are tiny, shrimp-like creatures often used as food for smaller fish. They’re a type of plankton and can be cultured at home.

Daylight Spectrum: This refers to the range of light that simulates natural daylight. It’s often used in aquarium lighting to support plant growth and make the tank look natural.

Dechlorinator: This is a chemical treatment that removes harmful chlorine from tap water, making it safe for your fish.

Decor: These are the decorative items you place in your tank, like fake plants, rocks, or driftwood. They offer hiding places for fish and add visual interest.

Decomposition: This is the process where organic materials, like dead plants or fish waste, break down into simpler substances. This is a natural process but needs to be managed in an aquarium.

Deficiency: In the context of aquarium plants, this term refers to a lack of necessary nutrients, which can lead to poor growth and discolored leaves.

Deionization (DI): This is a water purification method that uses special resins to remove mineral ions from the water, often used in marine tanks.

Denitrification: This is a process where beneficial bacteria convert harmful nitrates back into nitrogen gas, which then leaves the tank. It’s a less common but beneficial form of biological filtration.

Detritus: These are small particles of organic waste that accumulate on the bottom of your tank. Detritus can include fish waste, leftover food, and plant debris.

Detrivore: These are creatures that feed on detritus, helping to keep the tank clean.

Diatoms: These are single-celled algae that can form a brownish coating on various surfaces in a new or imbalanced aquarium.

Dissolved Organic Compounds: These are tiny bits of organic material dissolved in the water. High levels can make your water cloudy and decrease water quality.

Diurnal: These are animals that are most active during the daytime.

Dorsal Fin: This is the fin located on the back of a fish. It helps the fish to stabilize itself while swimming.

Dosing Pump: This is a device that automatically adds a specific amount of liquid—like fertilizers or medication—to your tank at set intervals.

Drip Acclimation: This is a method for gradually introducing new fish to your tank’s water. You slowly drip water from the tank into the container holding the new fish to help them adjust to the new water conditions.

Dutch Aquarium: This is a style of aquascaping that aims to create a densely planted, colorful underwater garden. It often involves arranging plants in terraces or rows for visual effect.


Eco-Complete: This is a type of substrate that’s loaded with beneficial bacteria and minerals. It’s designed to promote plant growth and help cycle your aquarium more quickly.

Ecosystem: This term refers to the interdependent community of living organisms and the physical environment within your aquarium. It’s a balanced system where plants, fish, and bacteria all play roles in maintaining water quality.

Egg-Layer: These are fish species that reproduce by laying eggs, rather than giving live birth. If you’re interested in breeding fish, it’s important to know whether your species is an egg-layer.

Electrical Conductivity (EC): This is a measure of how well your water conducts electricity, and it’s often used as a rough estimate of water purity and mineral content.

Evaporation: This is the process where water turns into vapor and leaves the aquarium, lowering the water level. You’ll need to add more water occasionally to make up for the loss.

External Filter: This is a filter that sits outside of the tank and is usually more powerful than internal filters. It pumps water out of the tank, filters it, and then pumps it back in.

Extruded Pellets: These are a type of fish food made by cooking a mixture of ingredients under high pressure. They’re generally well-balanced and offer good nutrition for your fish.

Eye Infection: This is a condition where a fish’s eye becomes cloudy or swollen. It’s usually a sign of poor water quality or bacterial infection and requires immediate attention.

Euthanization: This is the act of humanely ending a fish’s life, often when it’s suffering from an incurable illness or injury. There are specific methods designed to cause the least amount of stress to the fish.

Enriched Substrate: This is a layer of substrate that’s packed with nutrients specifically for the benefit of aquarium plants. It’s typically placed at the bottom of the tank beneath a layer of gravel or sand.

Elodea: This is a common aquatic plant used in freshwater tanks. It’s easy to grow and provides good cover for fish, although it’s more about the plant than a term.

Erosion Feeder: These are fish that scrape algae and other material off rocks and driftwood. They serve as a natural cleaning crew but are less relevant for planted tanks.

Effluent: This refers to the waste water that comes out of your filter. In more advanced setups, you may need to treat or dispose of this water properly.

Emergency Generator: This is a backup power source designed to keep your tank’s life-support systems running during a power outage. It can be a literal lifesaver for your fish.

Epsom Salts: These are magnesium sulfate salts sometimes used to treat certain fish ailments. Always consult a vet or an expert before using them.

Emersed: This term describes plants that grow partially out of the water, with their roots submerged and their leaves above the water surface.

Egg Crate: This is a plastic grid often used in lighting fixtures, but in aquariums, it’s commonly used to separate areas or support rock formations.

Enzyme: These are proteins that speed up chemical reactions, like the decomposition of waste in your tank. Some water treatments include enzymes to help maintain water quality.


Fairy Shrimp: Despite its magical name, the fairy shrimp is actually a large species of brine shrimp often raised as a nutritious food source for other fish in the aquarium.

Feeder Fish: These are small, less expensive fish bred specifically to be food for larger, carnivorous fish in your tank. While a convenient food source, they should be used cautiously due to the risk of transmitting disease.

Feeding Ring: This is a handy floating device that keeps floating food contained in one area, making it easier for your fish to eat and reducing the mess of food drifting all around the tank.

Filter: One of the most important components of an aquarium, the filter removes physical waste and chemical impurities from the water while helping to circulate it. It can use different types of filtering media like sponges or activated carbon for more effective cleaning.

Filter Feeder: These are organisms like certain shrimp and clams that feed by trapping microscopic particles or tiny creatures from the water. They essentially act as natural water cleaners.

Filter Floss: Think of this as the sponge or scrub of your filter. It’s made from a material like polyester and is used to catch even the smallest bits of debris, helping to keep your water clear.

Filter Media: These are the materials placed inside your filter that do the actual work of trapping unwanted substances. Types include mechanical media like sponges, biological media like ceramic rings, and chemical media like activated carbon.

Flake Food: This is one of the most common types of fish food and is often made from a mix of fish meal, brine shrimp, and vitamins. The food floats on the water’s surface and is easy for most fish to eat.

Fluidized Bed Filter: A bit like a sand tornado in a tube, this type of filter uses sand that’s kept in constant motion by water flow. The sand provides a home for beneficial bacteria that help clean the water.

Footprint: This refers to the actual size of the bottom of your aquarium or stand. Knowing the footprint is important for ensuring your tank fits into your designated space and that the stand can support its weight.

Frozen Food: These are foods that are minimally processed and then frozen to maintain their nutritional value. Choices range from bloodworms to tiny shrimp, offering a good variety for fish diets.

Fry: These are baby fish that have just hatched from eggs. They’re extremely delicate and require specialized care, including finely crushed food and stable water conditions.

Fertilizer: This is a substance rich in essential nutrients for plants. It can come in liquid or granular form and is used to promote healthy plant growth in planted tanks.

Finnage: This term refers to the arrangement, shape, and size of a fish’s fins. Understanding the normal appearance of your fish’s finnage can help you quickly identify any signs of disease or stress.

Fishless Cycling: This is the practice of cycling a new aquarium using ammonia or decaying matter instead of live fish, to establish beneficial bacteria without harming any fish.

Fungus: This term refers to fungal growth that can occur in aquariums, often as a result of poor water quality. It appears as white, cotton-like growths on fish or decorations and requires immediate treatment.

Freshwater Salts: These are specific types of non-iodized salts used to treat various fish diseases and conditions. Always consult with a vet or fish expert before using any salt treatments.

Flow Rate: This is the speed at which water is pumped through the filter, typically measured in gallons per hour (GPH). The flow rate you need depends on the size and type of your aquarium.


GH (General Hardness): This acronym stands for the total amount of calcium and magnesium dissolved in your aquarium water. Knowing your water’s GH is crucial because different fish and plants have specific hardness requirements for optimal health. It’s typically measured in either parts per million (ppm) or degrees of general hardness (dGH).

Gills: These are the aquatic equivalent of lungs for fish. Gills are specialized organs that allow fish to extract life-giving oxygen from water while expelling waste carbon dioxide back into the water.

GPH (Gallons Per Hour): This is the measure of how much water your filter pump or powerhead can circulate in one hour. The right GPH is essential for keeping your aquarium water clean and well-oxygenated.

Gravel Vacuum: This is basically a cleaning tool that consists of a hard plastic tube attached to flexible tubing. You use it to create a siphon, which allows you to suck up waste and debris that have settled at the bottom of your gravel or substrate.

Green Water: This is not a fancy aquarium cocktail but rather a sign of an algal bloom. When you have too many floating microalgae in your water, they can give it a greenish tint. Although not harmful in moderate amounts, excessive green water can be a sign of an imbalanced aquarium.

Grow Out Tank: This is a specialized aquarium used for raising young fish until they’re large enough for sale or transfer to a larger tank. It’s an essential part of breeding programs or for those who are serious about raising juvenile fish to adulthood.

Glass Lid: This is a transparent cover made of glass that sits on top of your aquarium. It’s useful for reducing water evaporation and preventing fish from leaping out, while still allowing light to penetrate for plants and visibility.

GFCI (Ground-Fault Circuit Interrupter): This is a device that automatically cuts off electrical power to your aquarium equipment if it detects any imbalance in the electrical current. It’s an important safety feature to prevent electrical shocks.

Gel Food: This is a type of fish food that’s formulated as a gel. It can be particularly beneficial for fish species that prefer softer foods, and it usually contains a mix of proteins, carbohydrates, and essential nutrients.

Gravel: This is a type of substrate often used at the bottom of freshwater aquariums. Gravel comes in various sizes and colors, and it’s important to choose one that is appropriate for the fish and plants you’re keeping.

Guppy Grass: Despite its name, this is a type of aquatic plant, not a type of fish. Guppy Grass is popular for providing hiding spots for small fish and breeding grounds for certain species.

Glutaraldehyde: This is a liquid chemical often used as an algae killer or as a component in liquid fertilizers. While effective, it should be used with caution, as it can also be harmful to some aquatic life.

Gazebo Effect: This is an aquarium design concept where the decorations and plants are arranged to create a focal point, often in the center of the tank, which draws the eye and enhances the aesthetic appeal of the aquarium.


Habitat: This term describes the natural surroundings where a plant or animal lives. In aquariums, the term can refer to the overall setup, which mimics the natural environment of the fish and plants you are keeping.

Hang-on-the-Back Filter (HOB): This is a type of power filter that sits externally, hanging off the edge of your aquarium. It draws water up through an intake tube, filters it through a series of media like sponges or activated charcoal, and then returns the cleaned water back into the aquarium.

Hard Water: This is water that has a high concentration of minerals, particularly calcium and magnesium. Measured in degrees of general hardness (GH), hard water is usually considered to have a GH between 10-25 GH or 166-417° dGH. Hard water can affect both the health of your fish and the effectiveness of your equipment.

Hardscape: These are the non-living, solid elements you put in your aquarium—like rocks, stones, or driftwood—that contribute to the overall look and feel of your tank’s landscape. Hardscape items can also serve as hiding places or territorial boundaries for your fish.

Heater: This is a submersible electrical device that keeps your aquarium water at a stable, preset temperature. Most heaters have an internal thermostat that turns the device on and off depending on the water temperature, which is crucial for the well-being of your fish.

Herbivore: These are creatures whose diet mainly consists of plant material. In an aquarium setting, they might munch on algae, aquatic plants, or specialized plant-based fish food.

Hospital Tank: This is an isolation tank where you can place sick or injured fish away from the main aquarium. Here, you can treat them without affecting the other inhabitants and monitor their recovery more closely.

Hybrid Fish: This term refers to a fish born from the crossbreeding of two different species. The practice of creating hybrid fish is contentious; while some see it as a way to develop new, hardy, or more attractive strains, others condemn it for ethical or ecological reasons.

Hydrometer: This is a tool used to measure the specific gravity or salinity of water. While more commonly used in saltwater tanks, it can be employed in freshwater setups that require specific brackish conditions.

Hydroponics: This is a method of growing plants without soil, often using nutrient-rich water instead. While not traditional in freshwater tanks, some setups integrate hydroponic systems to cultivate terrestrial plants using the nutrient-rich aquarium water.

Hydraulic Head: This is the measure of the pressure or force that pushes water through your aquarium’s filtration system. Understanding the hydraulic head is crucial when setting up complex filtration setups or when calculating the strength of pumps needed.

Heavily Planted: This refers to an aquarium where a large portion of the tank’s space is filled with live plants. The abundance of plants provides natural filtration, oxygenation, and sometimes even food for the tank’s inhabitants.

High-Tech Tank: This term describes an aquarium that employs advanced equipment such as CO2 injection systems, specialized lighting, and automated dosing pumps to provide optimal conditions for plant growth and fish well-being.


Indian Almond Leaves (Terminalia catappa): Also known as catappa leaves, these are dried leaves from the Indian almond tree. When added to an aquarium, these leaves release beneficial tannins and anti-inflammatory flavonoids into the water. They also serve as a food source for fry and ornamental shrimp, helping mimic their natural environment.

Insectivore: This term describes any organism whose diet primarily consists of insects and their larvae. In the aquarium world, some fish and invertebrates are insectivores and may require specialized diets to meet their nutritional needs.

Internal Filter: This is a type of power filter that is fully submerged and usually situated against the aquarium’s back wall or in a corner. It can contain different types of media—mechanical, biological, or chemical—to help keep your tank water clean and safe for your aquatic pets.

Invertebrates: These are animals lacking a backbone or vertebral column. In a freshwater aquarium setting, this group can include creatures like snails and shrimp, which often add to the tank’s biodiversity and help with cleaning and algae control.

Infusoria: These are tiny aquatic organisms such as algae and protozoa, which are commonly found in freshwater ponds. They are often cultured and used as a first food for very small fry that can’t eat larger food particles yet.

Iwagumi Tank: Translated to mean “rock formation” in Japanese, this is a specialized style of aquascaping where rocks and stones are the main focus. They are meticulously arranged following specific aesthetic guidelines to create a serene and natural-looking underwater environment.

Isolation Tank: This is another term for a hospital or quarantine tank, used for isolating new, sick, or injured fish from the main aquarium for observation and/or treatment.

Inlet and Outlet Pipes: These are crucial parts of your aquarium’s filtration system. The inlet pipe sucks in water to be filtered, while the outlet pipe returns the cleaned water back to the tank. Understanding the flow rate and positioning of these pipes is crucial for effective filtration.

Iron (Fe): This is a microelement essential for the proper growth of aquatic plants. Iron deficiency usually results in yellow leaves and poor growth. It is often added through specialized fertilizers or root tabs.

Illumination: This refers to the artificial light source in your aquarium, usually provided by LED lights, fluorescent tubes, or other specialized aquarium lights. Proper illumination is critical for both plant growth and the well-being of your aquatic pets.

In-line Heater: Unlike standard heaters that are submerged in the tank, in-line heaters are connected to the external filtration system. Water is heated as it passes through the unit and then returned to the aquarium.

Ion Exchange: This is a process often used in water softening where ions of calcium and magnesium are exchanged for sodium ions using a special type of resin. While not commonly used in most freshwater setups, it’s crucial in those requiring very soft water.


Jungle Aquarium: This is a specific style of aquascaping that is an offshoot of the nature aquarium concept. The focus here is on creating a lush, dense planting arrangement that resembles a submerged jungle. Expect to see bushy and tangled plant growth that creates hiding spots and a visually appealing, complex environment for fish and invertebrates.

Java Moss: Although not an animal, it’s worth noting this plant as it’s one of the most popular choices for freshwater aquariums. It’s easy to grow and provides an excellent environment for both small fish and invertebrates to hide and forage.

Juvenile: This term refers to fish or invertebrates that have passed the fry stage but haven’t yet reached full maturity. In this phase, the creatures may require special care and diet to support their growth.

Jacuzzi Effect: This is a somewhat humorous term that refers to the powerful current generated by some types of aquarium filters or powerheads. If too strong, this current can make it difficult for fish to swim comfortably, essentially making them feel like they are in a jacuzzi.

Jumper: Some fish are known for their ability to leap out of the water. A “jumper” is any fish that has a tendency to jump, requiring you to have a secure lid on your aquarium to prevent any accidental escapes.

Jet: This refers to a focused stream of water, often created by a powerhead or specialized nozzle in an aquarium setup. Jets are used to create currents and can also help prevent dead zones where detritus might accumulate.

Jar Method: A form of culturing live food, like brine shrimp or algae, in jars. This provides a consistent and renewable source of live food for aquarium inhabitants, often used by hobbyists who take a DIY approach to their aquarium’s needs.

Jug Method: Similar to the jar method, this involves using a larger container, usually a jug, to prepare water additives or conditioners before they are added to the main aquarium. This ensures that everything is well-mixed and evenly distributed when introduced into the aquarium environment.


KH (Carbonate Hardness): This is a measurement that helps you understand the buffering capacity of your aquarium water. Specifically, it quantifies the amount of carbonate and bicarbonate ions dissolved in the water. This information is important for maintaining stable pH levels and is often expressed as parts per million (ppm) or degrees of carbonate hardness (dKH).

Krill: These are tiny, shrimp-like marine animals that form large swarms in the ocean. They are commonly harvested and processed to be included in high-quality commercial fish foods. Krill provides essential nutrients and is especially popular for enhancing the color of aquarium fish.

Koi Pond: Although not strictly an aquarium term, koi ponds are freshwater environments designed to house koi fish. While the care principles are different, many of the same water quality considerations apply to both aquariums and koi ponds, making it relevant to those interested in all forms of aquatic husbandry.

Kidney Bowl: This is a small, usually plastic or metal bowl that is kidney-shaped, used in the aquarium hobby for transferring small amounts of water, fish, or invertebrates. It allows for easy pouring and can be particularly useful when acclimating new species to your tank.

Knots: Refers to how some hobbyists tie aquatic plants to rocks or driftwood in their aquariums. The term can also refer to the speed of water flow in marine contexts but is less commonly used in freshwater aquarium parlance.

Kits: These are all-in-one packages sold by aquarium product manufacturers that usually include essential equipment like filters, heaters, and sometimes even lighting and a tank. They offer a convenient way to set up a new aquarium but may require upgrades for more advanced or specific needs.

Keel: This term refers to a ridge or an elevated part running along the body of some types of aquatic creatures, similar to the keel of a boat. In the context of a freshwater aquarium, it might be referenced when discussing the body shape of specific fish or invertebrates.

Kettle: In aquarium contexts, this usually refers to a container used for mixing and preparing water treatments or food recipes. Some aquarists use a separate kettle to heat water to a specific temperature for various purposes, such as hatching brine shrimp eggs.


Labyrinth Fish: These are a group of fish, primarily from Southeast Asia, belonging to the family Anabantoidei. Species like Bettas and Gouramis are examples. What sets them apart is their labyrinth organ, which acts like a lung, allowing them to gulp air from the surface. This is in addition to the oxygen they can extract through their gills, making them quite versatile in terms of oxygen absorption.

Larvae: The term refers to the juvenile form of many insects and other invertebrates, which undergo a transformation as they mature into adults. In the context of an aquarium, some aquatic insects might appear in this stage and could serve as food for fish or other creatures. It’s important to note that the larval stage can look very different from the adult form and may require different environmental conditions.

Lava Rock: This is a type of rock formed from cooled volcanic lava. It’s often used in aquariums both as a decorative item and as a biological media due to its porous nature, which allows beneficial bacteria to grow and flourish.

Lateral Line: This is a special row of sensory organs that runs down both sides of a fish’s body. The lateral line allows fish to detect movements and vibrations in the surrounding water, which can be crucial for navigation and avoiding predators.

Lid: This is the cover that goes on top of an aquarium. Lids are useful for multiple reasons—they help reduce water evaporation, keep the equipment and lights dry, and most importantly, prevent fish or other creatures from jumping out of the tank. They can be made from various materials like plastic or glass.

Livestock: In aquarium lingo, livestock refers to the fish and invertebrates that you keep in your aquarium. This term encompasses all of the living creatures that aren’t plants.

Liquid Fertilizer: This refers to concentrated solutions containing essential macro and micronutrients that are added to the aquarium water. These nutrients are absorbed by live plants, aiding in their growth and overall health.

Livebearer: This term is used to describe fish species that give birth to live young instead of laying eggs. Guppies, mollies, platies, and Endler’s livebearers are popular examples. Livebearers are often easier to breed and care for compared to egg-laying species.

Light Timer: An electronic or mechanical device that you can set to automatically turn your aquarium lights on and off at specific times, helping to regulate the day-night cycle for your aquatic pets.

Low Tech Tank: An aquarium setup that does not rely heavily on advanced technology like CO2 injection or specialized lighting. These tanks are often easier to maintain but may be limited in terms of the species of plants and fish that can be kept.

LFS (Local Fish Store): An abbreviation often used among aquarists to refer to their nearby aquarium or pet store that specializes in fish and aquarium supplies.

Live Food: Refers to living organisms like brine shrimp, daphnia, or worms that are used as food for fish. Live food is considered more nutritious and stimulating for the fish but can also come with risks like disease transmission.

LED Lighting: A type of lighting that is often used in aquariums for its energy efficiency and low heat output. LED lights can be tailored to emit specific wavelengths, which can benefit both plants and fish.


Macronutrients: These are the nutrients that aquatic plants consume in larger amounts to fuel their growth. Common examples include nitrate (NO3-), phosphate (PO4), and potassium (K). They are crucial for processes like photosynthesis and cell development. If you have a planted tank, you’ll need to make sure these nutrients are adequately supplied.

Mechanical Filtration: This is one of the three main types of filtration in an aquarium. It works by forcing water through a physical medium, like sponge or floss, which traps and removes solid particles such as detritus, uneaten food, and plant material. This is essential for keeping the water clear and reducing the load on biological and chemical filtration.

Media Bag: Think of this as a small, mesh pouch that you can fill with various types of filter media, like activated carbon or ceramic rings. You then place this bag inside your filter, where it helps to remove unwanted substances from the water. It’s like a customizable pocket for your filter.

Micronutrients: Unlike macronutrients, micronutrients like iron, manganese, and zinc are needed in much smaller amounts by plants. They are still essential for certain physiological processes but are consumed much less rapidly. They’re often included in comprehensive liquid fertilizers for planted tanks.

Mid-water Fish: These are fish that tend to spend most of their time swimming and feeding in the middle layer of the water column. They’re not bottom-dwellers or surface-skimmers but prefer the in-between. Examples would be species like tiger barbs and neon tetras.

Mouthbrooder: This is a breeding strategy used by some fish species where fertilized eggs are kept in the parent fish’s mouth until they hatch. Depending on the species, it could be either the male or the female that holds the eggs. This technique helps protect the eggs from potential predators and improves their chances of survival.

Maturation Cycle: Also known as the aquarium cycle, this is the process of establishing beneficial bacteria in a new aquarium. These bacteria help break down harmful ammonia and nitrite, converting them into less harmful substances. Skipping or rushing this cycle can result in harm to your fish.

Mineralization: The process of breaking down organic matter, like decaying plants and fish waste, into inorganic minerals that plants can use. In the context of an aquarium, this often happens in the substrate and is facilitated by microorganisms.

Moonlight: Some aquariums have special ‘moonlight’ LED settings that mimic the dim light of the moon. This can help simulate a natural day-night cycle for your fish and can also make the tank more visually appealing at night.

Mopani Wood: A popular type of aquarium wood that’s known for its two-tone coloration. It’s often used for aesthetic purposes and can also serve as a surface for beneficial bacteria and aquatic mosses to grow on.

Magnetic Cleaner: A two-piece cleaning device with magnets on each piece; one goes inside the tank and the other stays outside. By moving the outer magnet, you can clean algae and grime off the glass without getting your hands wet.


Nature Aquarium: A style of aquascaping that aims to replicate natural landscapes, either aquatic or terrestrial. Unlike the Dutch style, which looks more like a meticulously designed garden, the Nature style aims for a more organic, wild look, utilizing live plants, rocks, and driftwood in a way that mimics nature.

Nitrate (NO3-): This is the final and least toxic byproduct of the nitrogen cycle. Beneficial bacteria convert nitrite into nitrate, which is generally less harmful to fish and can be removed or diluted through regular water changes or absorbed by plants as a macronutrient.

Nitrite (NO2-1): This chemical is one step along the nitrogen cycle and is created when beneficial bacteria consume ammonia. Nitrite is highly toxic to fish and should ideally be at zero in a well-cycled, balanced aquarium.

Nitrogen Cycle: Think of this as the biological filtration system of your tank. It’s a natural process where beneficial bacteria consume toxic ammonia produced by fish waste and other organic material, converting it into less harmful substances like nitrite and eventually nitrate.

Nocturnal: Refers to organisms that are most active during the nighttime. Some aquarium fish and invertebrates are nocturnal, so you might not see them much during the day.

Nuchal Hump: Also known as a “Kok,” this is a fleshy protrusion on the forehead of certain fish, most commonly seen in male cichlids. It’s often a sign of sexual maturity and can become more pronounced during breeding seasons.

Nitrifying Bacteria: These are the beneficial bacteria responsible for converting ammonia into nitrite and nitrite into nitrate in the nitrogen cycle. They colonize surfaces in the aquarium like the filter media, substrate, and decorations.

Neutral Water: Water with a pH level close to 7, which is considered neither acidic nor alkaline. Some fish species prefer neutral water, and it’s often a good starting point for many community aquariums.

Nano Tank: This term refers to small aquariums typically ranging from 2 to 10 gallons in capacity. Due to their small size, they require more frequent maintenance but are often chosen for their convenience and aesthetic appeal.

Nets: Specialized nets used for various purposes in aquarium care. There are brine shrimp nets for collecting tiny foods, larger nets for moving fish, and specialized nets with finer mesh for handling delicate or smaller species.

Nutrient Export: The removal of excess nutrients like nitrates and phosphates from the aquarium, usually achieved through water changes, protein skimming, or by using plants and algae that absorb these nutrients.

New Tank Syndrome: This occurs in newly set up aquariums where the nitrogen cycle has not yet stabilized. Fish waste generates ammonia, but there aren’t enough beneficial bacteria to process it, leading to elevated levels of ammonia and nitrite, which are toxic to fish.


Omnivore: Creatures that have a varied diet, consuming both plant and animal matter. In an aquarium setting, an omnivore might munch on algae or vegetables as well as eat meaty foods like brine shrimp or fish flakes.

Osmoregulation: This is how an organism balances fluid and electrolytes in and out of its cells. For freshwater fish, this is particularly crucial because they live in an environment where the water is less salty than their internal fluids. They are continually absorbing water and have to excrete the extra through their urine to maintain balance.

Oxygenation: This term refers to the process of increasing the levels of dissolved oxygen in the water. In aquariums, oxygenation is often achieved using air pumps, surface agitation, or specialized oxygenating equipment. Fish and other aquatic life use this dissolved oxygen to breathe.

Overflow Box: A device used in aquariums with sump filtration systems. It allows water to flow from the main tank to the sump tank below it safely. It is especially crucial in saltwater systems but can also be used in freshwater setups.

Overstocking: Refers to having too many fish or aquatic animals in an aquarium, exceeding its carrying capacity. Overstocking can lead to a variety of problems, including poor water quality, increased disease susceptibility, and stress among the aquarium inhabitants.

Overfeeding: The act of giving more food to the aquarium inhabitants than they can consume, leading to uneaten food that decomposes and adversely affects water quality.

Ozonizer: A device that generates ozone gas (O3) and injects it into aquarium water to kill bacteria and parasites, as well as break down harmful waste substances. While more commonly used in marine tanks, it can also be used cautiously in freshwater setups.

Output Nozzle: The part of a filter where the cleaned water is returned to the aquarium. The design of the nozzle can often be adjusted to direct water flow and improve circulation within the tank.

Ornaments: Decorative items that are placed in an aquarium for aesthetic purposes. While not biologically essential, they add visual interest and may offer hiding spots for fish. It’s important to ensure that any ornaments used are made from materials that are safe for aquarium use.


Parasite: Organisms that live on or inside a host from a different species and draw nutrients or other benefits at the host’s expense. In an aquarium setting, parasites can be responsible for various diseases and need to be treated promptly to avoid infecting other fish.

Peat Moss: A type of organic matter often used as substrate or chemical filter media in aquariums. It naturally softens and acidifies the water, making it suitable for fish that prefer softer, more acidic conditions.

Pectoral Fins: These are the fins located on either side of a fish’s body near the head. They are primarily used for steering, maintaining balance, and slow movements in the water.

Pelvic Fins: Located on the lower side of the fish’s body, these fins assist in stabilization during swimming. They may also have other specialized functions depending on the species of fish.

pH (per Hydrogen): A scale used to measure the acidity or alkalinity of a liquid. The pH scale ranges from 0 to 14, with 7 being neutral. It’s important to monitor and maintain the pH levels in an aquarium to keep the fish healthy.

Phosphate (PO4): An organic compound composed of phosphorus and oxygen, it is a waste product that can accumulate in aquariums from fish waste, decaying plant material, and uneaten food. Phosphates are used by plants but can cause algae blooms if levels are too high.

Photosynthesis: The biochemical process by which plants use light to convert carbon dioxide and water into glucose and oxygen. Aquarium plants rely on photosynthesis for growth, and this process also contributes to oxygenation of the water.

Plankton: A diverse collection of tiny aquatic organisms that float in the water and are mostly incapable of swimming against currents. While plankton is more commonly found in natural water bodies, some specialized aquarium setups might incorporate plankton as a live food source.

Potassium (K): An essential element for plant growth, potassium aids in processes like osmoregulation, enzyme activation, and cell wall strength.

PPM (Parts Per Million): A unit of measurement indicating the concentration of a particular substance within a liquid. It is often used to measure levels of various chemicals or nutrients in aquarium water.

Power Filter: A type of aquarium filter that uses an electric pump to move water through mechanical, chemical, or biological filter media. These are commonly used in both beginner and advanced setups.

Powerhead: A submersible pump placed inside the aquarium to enhance water circulation and oxygenation. Powerheads are especially useful in tanks with live plants or reef setups to simulate natural water movement.

Protein Skimmer: Although more common in marine aquariums, some advanced freshwater setups might employ a protein skimmer. This device removes organic compounds, including fish waste and food particles, by creating bubbles that attract and trap these substances.

Pythons: Not to be confused with the snake, a Python in the aquarium context refers to a specific brand of water changer or siphon used for aquarium maintenance. These make it easier to change water and siphon out waste.


Quarantine Tank: A separate aquarium set up to isolate new or sick fish from the main aquarium population. The purpose of this tank is to observe new arrivals for signs of illness and to treat any diseases without affecting the established ecosystem of the main tank.

Quick-Start Solutions: Commercially available bottled products designed to accelerate the process of establishing beneficial bacteria in a new aquarium. These solutions can help to jump-start the nitrogen cycle, making the environment safer for fish more quickly.

Q-Tip Test: A practical test where a cotton swab (Q-Tip) is used to gently touch algae or other substances on aquarium decorations or walls. Depending on how easily the substance comes off or its color, one can gauge what type of algae or deposit it is.


Reverse Osmosis (RO): A water purification method often used in freshwater aquariums to remove contaminants. It forces water through a semipermeable membrane, resulting in water that is free from most dissolved salts, bacteria, and contaminants.

Rimless Tank: A type of aquarium that lacks a plastic or metal frame around its top edge. This is purely for aesthetic reasons and provides a clean, unobstructed view into the aquarium.

Root Tab: Small, nutrient-rich tablets that can be buried in the substrate near aquatic plants. The roots of the plants can then absorb the nutrients, promoting healthier growth.

RO/DI: Stands for Reverse Osmosis and Deionization. A water purification process combining RO and DI to produce very high-quality water for sensitive aquatic life and plants.

Rubbermaid Tub: Often used as a makeshift quarantine or hospital tank. Rubbermaid tubs are easy to set up and are inexpensive compared to glass or acrylic aquariums.


Salinity: Amount of salt dissolved in a sample of water.

Sand Bed: A type of aquarium substrate made up of sand; usually used in tanks that house species which prefer finer substrates or are prone to digging.

Scaping Tools: Specialized tools used for aquascaping, or arranging the plants and decorations in an aquarium; these can include tweezers, scissors, and spatulas for precise placement and trimming.

Schooling Fish: Fish that live in a group with others of the same species and swim together in a coordinated and directional manner.

Scavenger: Organisms that feed on dead or decaying material in the aquarium; they help in breaking down waste and keeping the tank cleaner.

Seasonal Adjustment: Changes made to aquarium conditions, such as temperature or photoperiod, to simulate natural seasonal changes and possibly trigger breeding behavior in fish.

Shoaling Fish: Fish that live together in a group for social purposes but don’t move together in a coordinated way.

Shock Treatment: A sudden and drastic change in the water conditions, typically temperature or chemical composition, used as a last resort to treat severe diseases or parasite infestations.

Silicone: Synthetic compound used to seal pieces of aquarium glass together and make the seams watertight.

Sintered Glass: Small beads of glass that have been heated to just below the melting point and pressed together to form a rough and porous surface; placed in media bags and used as a biological filtration media that houses beneficial bacteria.

Siphon: Method for pumping water; a tube draws water from the original container using the pull of gravity and pours it into another container kept at a lower level; primary way aquarists drain water from a display tank for water changes.

Slime Coat: Protective layer of mucus that covers the skin and scales of fish; important part of the immune system that wards off bacteria and viruses in the surrounding environment.

Snail Trap: A device used to catch and remove unwanted snails from the aquarium; typically baited with food to lure the snails inside.

Soft Water: Water with low levels of dissolved minerals, especially calcium and magnesium; soft water is generally preferred by certain types of freshwater fish and plants that come from environments with low mineral content.

Spawn: Release or deposit of eggs and sperm by fish and other aquatic organisms.

Spawning Mop: Synthetic yarn tied together to resemble the head of a string mop; mop is placed in the bottom of a tank so that when fish spawn, the eggs stick to the mop; when the mop is removed, the eggs stay on it and so can easily be moved to another tank to raise the fry.

Species Only Tank: Aquarium that houses only a single species of fish, usually because the chosen species can’t be housed with other kinds of fish.

Specific Gravity: Measure of how much salt is dissolved in a sample of water compared to pure water.

Spirulina: Green cyanobacteria that is commercially raised as a food additive for both people and fish.

Sponge Filter: Air driven filter that utilizes a large sponge for mechanical and biological filtration; a stream of bubbles from an air pump creates lift that draws water through the sponge.

Strainer: A mesh or perforated device typically placed at the end of a filter intake tube to prevent fish or large debris from being sucked into the filtration system.

Substrate: The layer of material, such as gravel, sand or soil, that covers the bottom of an aquarium.

Substrate Spawners (aka Egg Burier): Fish that dig a shallow depression in the substrate where they deposit their eggs; one or both parents will guard the nest until the fry hatch.

Substrate Vacuum: A specialized aquarium cleaning tool designed to remove detritus and waste from the substrate without significantly disturbing it.

Sump: Additional water tank, usually housed below the main display tank, that holds equipment like additional filters, heaters and pumps so that they don’t have to be kept inside the display tank; increases water volume of the tank allowing heavier stocking levels.

Supplement: Additional nutrients, minerals, or vitamins added to the aquarium water or food to enhance the health and vitality of aquatic plants and fish.

Surface Agitation: The disturbance of the water’s surface, often created by a filter’s output, air stones, or water pumps. This action helps to improve oxygen exchange and can also prevent surface film from forming.

Surface Area: Refers to the total area of the water’s surface in the aquarium, which affects the rate of gas exchange, including oxygenation.

Surface Skimmer: A device or component of a filtration system designed to remove floating debris and oils from the water’s surface, improving both water clarity and light penetration for plants.

Suspended Particles: Tiny bits of matter floating in the water column, which can make the water appear cloudy; these particles can be organic or inorganic and may require mechanical filtration for removal.

Syphon Starter: A device or method used to initiate the flow of water through a siphon tube for water changes; can be manual or automatic.


Tannins: Acidic organic compounds found in plants; tannins are brown in color and can dye aquarium water yellow or dark brown if present in significant amounts; tannins often leach from driftwood and Indian almond leaves; not toxic to fish but can make water more acidic.

Tap Water Conditioner: Chemical additives used to neutralize harmful substances like chlorine and chloramine found in tap water, making it safe for aquatic life.

Temperature Gradient: Variation in temperature within an aquarium; may be deliberately established for specific types of fish or occur unintentionally, affecting the health and behavior of fish negatively.

Test Kit: A set of chemicals and equipment used to measure various parameters of aquarium water, such as pH, hardness, ammonia, nitrite, and nitrate levels; crucial for monitoring the health of the aquarium ecosystem.

Thermometer: Device used to measure the water temperature in an aquarium; types include digital, stick-on, floating, and submersible thermometers.

Thermostat: Device that controls the operation of heaters or chillers in an aquarium; it ensures the water remains at a constant temperature by turning the heater or chiller on or off as required.

Thigmotaxis: Behavioral trait in which a fish stays close to the substrate or the sides of the aquarium; often indicative of stress or discomfort, but can also be normal behavior for bottom-dwelling species.

Timer: Electronic or mechanical device used to automate the on/off cycles for aquarium lights, heaters, or other electrical equipment.

Top Dwelling (aka Surface Dwelling): Fish that spend most of their time and feed at or near the surface of the water.

Trace Elements: Essential but minute quantities of elements required for the proper growth and health of aquatic plants and animals; commonly include elements like iron, zinc, and copper.

Trickle Filter (aka Wet/Dry Filter): Filter that pumps water out of the display tank to a sump below; water moves over a drip plate, a flat surface with many holes drilled in it, that diffuses the water so that it gently rains down on biological filter media below; water is then moved back up into the display tank by a return pump.

Tropical Tank: An aquarium set up to emulate a tropical environment; typically requires a heater to maintain a constant warm temperature.

Turbidity: Cloudiness or haziness in aquarium water due to suspended particles; can be caused by overfeeding, substrate disturbance, or bacterial blooms.

Turnover Rate: Measure of how many times in an hour a filter pump can move enough water to equal the total water volume of an aquarium; e.g., a 10-gallon aquarium using a filter that has a GPH (Gallons Per Hour) of 50 would have a turnover rate of 5.

TDS (Total Dissolved Solids): Measure of the combined content of all inorganic and organic substances in a liquid; expressed in milligrams per liter (mg/L) or parts per million (ppm); high TDS levels may indicate poor water quality and can be stressful to fish.


Undergravel Filter: Air-driven filters that utilize plastic filter plates that cover the entire bottom of the tank and are then covered completely with gravel substrate; air is pumped through tubes that attach to the plates, creating lift that forces water and waste through the gravel and through the plates below; beneficial bacteria grow on the gravel and filter harmful substances out of the water as it passes through.

Uninterruptible Power Supply (UPS): Backup power system used to provide electricity in the event of a power outage; critical for keeping essential aquarium equipment like filters, heaters, and air pumps running to maintain a stable environment for aquatic life.

Urea: Waste product of protein metabolism in fish; needs to be removed or converted into less harmful substances through biological filtration or water changes.

UV Clarifier: Similar to a UV sterilizer but generally less powerful; primarily designed to combat green water by clumping microscopic algae together so that they can be removed by mechanical filtration.

UV Sterilizer: Device that passes aquarium water through a tube that is exposed to a powerful UV lamp that can kill bacteria, viruses, and algae in the water column.


Water Change: Process of removing water from the aquarium and replacing it with clean water, often done to remove waste products and replenish essential minerals and trace elements; generally recommended to be done at regular intervals, such as weekly or bi-weekly.

Water Chemistry: The overall makeup of substances dissolved in aquarium water, which includes pH level, hardness, and concentrations of various ions; vital to the health and well-being of the fish and plants in the aquarium.

Water Conditioner: Chemical additive used to treat tap water and make it safe for aquarium use by neutralizing chlorine, chloramine, and some heavy metals; some also help protect fish by enhancing their slime coat.

Water Column: The open water of an aquarium between the surface and the substrate, often categorized into three zones: surface, mid-water, and bottom; each zone may be preferred by different species of fish or plants.

Water Flow: The movement of water within the aquarium, influenced by factors like filter output, air stones, and powerheads; important for proper oxygenation and distribution of nutrients.

Water Hardness: Measure of calcium and magnesium ions in water; can be classified as either “soft” or “hard”; important to maintain at appropriate levels for specific species of fish and plants.

Water Parameters: Measurements of dissolved compounds in a water sample; commonly include levels of ammonia (NH3), nitrite (NO2 -1), nitrate (NO3-), calcium (Ca), pH, and alkalinity; must be regularly checked to ensure a healthy aquarium environment.

Water Quality: Overarching term describing the cleanliness and chemical balance of aquarium water; influenced by factors like filtration, water changes, and waste production from fish.

Water Test Kit: Set of reagents and equipment used to measure various water parameters like pH, ammonia, nitrite, nitrate, and sometimes hardness and alkalinity; essential for monitoring water quality.

Wet-Dry Filter: A type of aquarium filtration system that exposes filter media to both aquarium water and air, typically used to enhance biological filtration; sometimes incorporated into a sump.

Wavelength: The distance between successive peaks in a wave of light; relevant in the context of aquarium lighting where different wavelengths are beneficial for plant growth and fish coloration.


Xenobiotics: Chemical substances that are foreign to a biological system, including man-made pollutants like pesticides, pharmaceuticals, or other synthetic chemicals. In the context of an aquarium, these are substances that are not naturally occurring in the water and could be harmful to fish and plants. They can enter the water through various means, including contaminated tap water, runoff, or even decaying matter.


Zeolite: Mineral used as a chemical filter media that removes ammonia from the water.