How to Clean Your Freshwater Fish Tank: Step-by-Step Water Change Guide for Beginners

Regular maintenance and small water changes are unavoidable if you want to keep happy and healthy fish. It doesn’t matter how good your filter is, you have to do it.

Allowing your tank to get dirty will cause a buildup of harmful bacteria and create the perfect environment for disease to thrive. And dealing with diseased fish is a lot harder that cleaning your aquarium once a week or every two weeks.

It’s much easier than you think to do a water change, and you can use this simple step-by-step guide to make it even easier.

Benefits of Cleaning Your Fish Tank

When I say clean your fish tank, what I’m actually saying is maintaining your tank through water changes.

And these water changes help restore and maintain a balanced aquarium by physically removing and diluting harmful chemicals while replenishing vital elements.

1. You’ll Reduce Harmful Compounds

Ammonia, nitrite, and nitrate can all be harmful to you fish.

During your initial Nitrogen Cycle, ammonia will turn to nitrite and nitrite will turn to nitrate, and most aquarium ecosystems lack the ideal conditions to efficiently process nitrate.

Nitrate isn’t harmful to your fish, unless you allow too much of it to build up.

Having high levels will stress your fish, making them vulnerable to disease and promoting poor growth and color development. Performing routine water changes will help control the levels of nitrate in your tank.

2. You’ll Remove Decomposing Waste Materials

Decaying organic waste in your aquarium will release toxic nitrogenous products, phosphates, and other harmful chemicals.

Leading to poor water quality. In extreme cases, they can create an acidic environment, compromising the buffering capacity of your water and harmful pH swings can occur.

3. You’ll Replenish Trace Elements and Essential Minerals

In the wild, there’s a consistent source of minerals, nutrients, and vitamins.

However, your filter will remove these vital elements or they’ll become depleted as your inhabitants use them to grow. Water change will provide a fresh supply necessary for proper growth.

Quick FAQs for How to Perform a Water Change

Do I have to take everything out of my fish tank?

No, you don’t want to do this…

It creates extra work and a large mess you don’t have to deal with. Every surface in your aquarium will grow some beneficial bacteria, and removing your decorations may kill off some of this bacteria and reduce the quality of your filtration for a while.

Should I remove the Fish?

No, you don’t need to remove the fish when you perform your regular 10-15% water changes.

You’re going to make more work for yourself than you need to, and is going to be extremely stressful for your fish. It could even cause physical injuries.

Now we’ve got the two common questions out of the way, let’s start the step-by-step guide.

Step-by-Step Guide: How to Perform a Water Change & Clean Your Aquarium

Let’s get into it, shall we?

Step 1: Get Your Equipment Ready

Equipment needed to clean an aquarium

Start by making sure you’re fully prepared and have all necessary equipment:

Step 2: Prepare Your New Tank Water

Preparing aquarium water a night before changing the water

I recommend doing this the night before and here’s why:

If you’re using tap or faucet water, it’s likely to have a lot of unwanted heavy metals, toxins and chlorine which can harm your fish. And it’s probably going to be the wrong temperature.

So what I recommend you do is fill up a bucket of water, add your water conditioner and allow it to sit over night. Doing this will help the chlorine evaporate and your water conditioner to make it aquarium safe.

It will also bring the water to room temperature and reduce the chance of your tank’s temperature having a dramatic change.

If you have any issues with water hardness or pH, you can also use this time to make changes to your new water and make sure the parameters are where you want them to be before adding it to your tank.

Key takeaway: Prepare your tank water with treatment a night before so it’s ready.

Step 3: Prepare Your Tank

If you have a water heater, you’ll need to position this so it’ll stay fully submerged while you’re siphoning out water.

If your heater becomes exposed, it could crack or overheat and break. I would suggest turning your filter off as well.

If it’s not possible to position your heater so it doesn’t become exposed, turning it off for a short amount of time will be fine.

You may also want to turn off your filter if it’s at risk of running dry (when your intake tube is at risk of being exposed by low water levels).

If air gets into your filter it can damage or break your system.

Key takeaway: Ensure none of your equipment risks becoming exposed when you remove your water.

Step 4: Clean the Sides of Your Aquarium and the Decorations

Get your algae pad or magnet and run it along the glass, be careful to scrub as little as possible.

It’s best to use a dedicated algae pad or magnet, not a sponge or scrubber from your kitchen. It could contain detergent or cleaning chemicals which will harm your fish.

If you have an acrylic aquarium, you’ll want to make sure whatever you use won’t scratch it.

Using your algae pad, lightly scrub your decorations. If you’re really struggling, you can remove them.

What you don’t want to do, is remove them and use bleach or boiling water. This is going to kill your beneficial bacteria or, if you use bleach, poison your fish.

Pro Tip: Do this before removing water so you will be able to remove algae debris with the gravel siphon. This will also help prevent the algae from spreading.

Step 5: Siphon the Water and Clean the Substrate

Siphoning aquarium water

Start by siphoning your tank’s water directly into your dedicated bucket. It’s best to buy a bucket purely for this purpose as residue from soaps or detergents can be harmful to your fish.

Whilst you’re siphoning the water out, you’ll want to carefully go through the gravel to remove as much of the waste as possible.

If you use sand, don’t use the vacuum like a shovel. Only use the hose part and hold it approx one inch from the surface to suck up any waste. This will stop you from disturbing the sand.

Cleaning different substrates

If you’ve got very small fish, and you’re worried about sucking them up, you can use a never-worn stocking on the end of your siphon. Just make sure the mesh is large enough to let debris enter.

Siphon your water until 10-15% of your tank’s water has been removed into your bucket.

Pro Tip: Siphoning at and angle will prevent clogging as it allows the substrate to slide back out.

Step 6: Rinse Your Filter Media

Rinsing filter media

You’re not replacing your filter media. Doing that for a routine clean and water change would remove too much bacteria and upset the water chemistry in your tank, shocking your fish.

You’re just giving it a rinse if it’s excessively dirty.

And this is where your dedicated bucket of tank water comes in handy. Rinse them with the water in the bucket, not tap water.

Chlorine in the tap water will kill the beneficial bacteria living in your filter and you’ll have to start a new Nitrogen Cycle.

Pro Tip: Rinsing your filter media does not mean you never have to change it. Change it approximately every 3-6 months or if you notice a drop in performance. When you do, keep your new and old media together for a few weeks before removing the old one. It will give the new media time to colonize with beneficial bacteria.

Step 7: Add Your New Aquarium Water

Use a thermometer to confirm that the temperature is within the correct range for your tank.

A dramatic change in water temperature can kill your fish. If you’re happy with your water, carefully start refilling your aquarium.

And don’t forget, your fish need some space between the water and top of the tank so they have enough oxygen and carbon dioxide exchange to breathe.

Pro Tip: If you’re struggling to lift your bucket up to your tanks edge, consider buying a quality pump. You’ll want a pump that can push water at least 5 feet high using 10 feet of flexible tubing.

Step 8: Cleaning the Outside of Your Aquarium

Not essential, but it can make view your tank mates a lot more pleasurable. Only clean the outside of your tank with solutions which are designated as aquarium-safe. The ammonia fumes from standard cleaners can harm your fish.

Final Thoughts on Water Changes and Cleaning your Fish Tank

Regular water changes is one of the most important aspects of maintaining a healthy environment for your fish to thrive. And it’s not very difficult, just follow the simple steps provided.

Christopher Adams
Christopher Adams

Hey there, my name is Christopher and I'm the creator and editor of this site. I've owned successful aquariums for the past 23 years. My mission is to educate, inform, and entertain on everything that's fish.


  1. Thank you, set up my first aquarium, and this as given me the confidence to carry out my first watch change correctly and safely.

  2. I have struggled with my new tank for almost two mths and have been following fish sites on fb and they had me going in a million directions..needless to say i have murdered a few fish along the way ?…this is the first explanation of beginning and maintaining a fish tank that actually makes since!! Thank you soooo much!

  3. I wish I read this last week I would still have my fish , I enjoyed what I read and learned how to properly clean my tank , thanks you have been a great help.

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