I highly recommend sponge filters for your aquarium.
Doesn’t matter if you have them on their own or to boost your current filteration.
They add so much surface area for beneficial bacteria, they’re easy to set up and operate, and they’re cheap.
In this guide, I’ll show you how to get the best one for you, a way you can create your own high capacity filtration system for under $40, and review the best sponge filters available today.
What is a Sponge Filter?
A classic sponge filter really only has six parts: base, step, strainer, bullseye, lift tube and sponge.
At the very bottom is a round base. It’s weighted so the sponge filter doesn’t float.
Above the base is a small piece of tube known as the step. All it really does is act as a spacer so the bottom of the sponge is above the substrate.
Coming out of the step are two pieces of strainer. Basically, they form a small plastic pipe with slots running up and down that you can take apart in the middle.
They look a lot like the intake on a power filter.
The sponge itself fits over the strainers, the slots let water flow through.
The bullseye connects the strainers to the lift tube. It’s hollow on the inside with spokes that form an X. In the middle of the X is a hollow nipple and that is where you attach your airline.
Pro Tip: To reduce noise, attach a small piece of airline to the bottom of the bullseye so you can attach an airstone or diffuser that will sit inside the strainers. This makes the bubbles going through the sponge filter MUCH finer so the filter isn’t so loud.
Coming up from the bullseye is the clear lift tube. Bubbles run up the lift tube towards the surface of the water. The bubbles pushing up the lift tube creates suction that forces water through the sponge below.
Pro Tip: You can opt to attach a powerhead to the lift tube of your sponge filter for more powerful filtration.
Benefits: Who Are Sponge Filters Right For?
Let’s start by discussing what sponge filters offer.
It’s actually impossible to run a successful aquarium without biological filtration.
It’s just a matter of fact, fish pee and poop in the water that surrounds them. It’s gross, but true.
As fish waste breaks down in the tank, it puts off ammonia (NH3).
This really bad because ammonia is highly toxic.
It’s possible for the ammonia to just keep building and building, until the water is pretty much toxic and every fish in the tank will die.
Lucky for us, we have some helpers that make our tanks livable.
What is Biological Filtration?
Biological filtration is just a fancy way of saying that the byproducts of fish waste in the tank are converted from toxic substances to non-toxic ones.
It’s actually colonies of beneficial bacteria growing in our filters that detoxify waste.
These helpful microorganisms turn ammonia into nitrite (NO2 -1) and then nitrate (NO3-).
Nitrate is much less toxic, so it can be allowed to build up in the tank in between weekly water changes.
Pro Tip: The beneficial bacteria you need for your tank don’t just appear as soon as you set up the aquarium. It takes time and patience to get the nitrogen cycle going in your tank so that it can support fish.
Take a look at this article for steps on how to get your tank cycled and ready for fish and invertebrates.
These super helpful beneficial bacteria need a place to live, though.
They actually produce a natural kind of glue and attach to themselves to porous surfaces where’s there’s a lot of water flow.
Beneficial bacteria love sponge filters. All the tiny pores in the sponge provide a lot of surface area that the bacteria can attach to.
Beneficial bacteria are aerobic, meaning they need oxygen to live. So they need a constant supply of oxygen from water flowing over them.
Sponger filters are awesome for this because water flows through them so easily, providing the bacteria with the oxygen they need.
Basically, a sponge filter is like a luxury condo on the beach as far as beneficial bacteria are concerned.
Sponge filters aren’t just biofilters, they’re also effective mechanical filters. They’re great for grabbing any little particles and detritus in the water column.
They also trap a good amount of fish poop.
The first time you clean one of these out, you’ll be shocked by the amount of gunk that even a small sponge can hold.
Sponge filters also help aerate your tank, especially ones that use an airstone.
I’ve run 10 gallon tanks using only a sponge filter for aeration and it worked great.
In a bigger tank, it’s great to put a sponge filter on the end opposite your hang-on-the-back filter. This is especially great for long tanks.
Having flow on both ends of the tank helps eliminate dead spots and gets all the water in the tank moving.
Fry and Shrimp Safe
Using a sponge filter is a great idea for fry and/or shrimp tanks.
Tiny fry and shrimp can easily get sucked up by the intake of a hang-on-the-back or canister filter.
This can’t happen with a sponge filter since there’s nothing for them to get sucked into.
In fact, both shrimp and fry will often feed off the surface of a sponge filter, eating algae, trapped food, bacteria and other lovely gunk they find tasty.
Cycled Back Up Filter
Running sponge filters in your tank can really save your bacon in an emergency.
Hang-on-the-back and canister filters can suddenly conk out on you. It can be really bad if you don’t realize it right away.
It’s possible to not notice for a day or two, especially if you use a canister filter. The lack of waterflow can kill all the beneficial bacteria in the filter.
That can leave you in a really bad spot and facing going through a “fish in” cycle in your tank, putting your livestock at risk.
But, if you’re running a sponge filter, in addition to your hang-on-the-back or canister filter, you’ve always got a backup that is already full of beneficial bacteria.
They’re also easy to move from one tank to another if you need to.
Pro Tip: Just be aware, whenever you transfer anything from one tank to another, even between two of your own tanks, there is a risk of cross contamination. That means, if there is some sort of disease or parasite in one tank, it can hitch a ride into the new tank.
I’ve also used cycled sponges to kickstart the nitrogen cycle in a new tank.
That way, you can immediately have a filter that has a colony of beneficial bacteria, instead of going through a fishless cycle for several weeks.
Low Flow Tanks
Some species of fish, like Bettas, don’t really like a fast moving current in their tanks. This makes an air driven sponge filter the perfect choice.
It gives you aeration plus mechanical and biological filtration, without creating so much flow that the poor Betta gets blasted all over the tank.
Let’s say you’ve got a 20 gallon (75 liter) tank. You can buy the components to set up a sponge filter for less money than a quality hang-on-the-back.
6 pack of air diffusers (which will last you forever by the way)
Airline check valve
This can often come out to less than $30-40.
That gives you a filter, with a lot more biofilter capacity than a hang-on-the-back for less than most setups. Plus, it’s simple to set up and maintain, and it would be more reliable than a power filter.
Downsides of a Sponge Filter
As much as I love sponge filters, they do have some downsides.
No Chemical Filtration
There’s really no way to add chemical filtration to most sponge filters.
While I’m a big believer that you don’t need to run chemical filtration all the time, there are instances when it comes in really handy, like running carbon to remove medications.
Not the Best Looking
Yep, sponge filters are not going to win any beauty awards. They are kind of a big ugly thing inside the aquarium.
But, in my opinion, you can hide them pretty well with plants and decor.
A Note on GPH Rating
When you shop for sponger filters, you’ll see that they’re rated for different tank sizes. So one might be rated for “up to 10 gallons” and another is “up to 60 gallons.”
But what does this really mean?
It partly comes down to how much water can pass through the sponge in an hour. Gallons per hour (GPH) is important because water needs to flow through the sponge so that the beneficial bacteria living inside it can grab waste out of the water column and process it.
The other part of the equation is the size of the sponge. It’s not just how many gallons move through it, it also needs a big enough surface area to sustain the numbers of bacteria you need.
Pro Tip: The ratings on filters don’t take bioload into account, just the volume of water. The heavier the bioload, the more filtration you need.
More is More
For larger tanks, it may be a good idea to run several smaller sized sponge filters rather than relying on one big one. By running smaller sponges in multiple locations around the tank, you increase water flow and cut down on dead spots.
Also, several medium sized sponges can easily have a much greater surface area than just a single large sponge.
You can often run several sponges off of one air pump by using T-valves to split the airflow across multiple airlines.
My Reviews for the Best Sponge Filters
Now you know more about what sponge filters offer, you can use my reviews to make an informed decision on which one is best for you.
1. Aquaneat Aquarium Sponge Filter
The Aquaneat is your classic sponge filter rated for up to 60 gallons. It’s pretty big, so probably best to put it in a 20 gallon (>75 liters) or bigger.
I like that it comes with some extras, especially the check valve. You’ll still need to get some more tubing and an air diffuser, but overall, this is a good kit.
Pro Tip: Non-return check valves are VERY important. If the power goes out, water will travel up the airline and can end up in your water pump, ruining it. A check valve lets air flow out, but doesn’t let water flow back in. I recommend check valves for any airline you run to protect your pump.
A check valve comes with this filter, but may not come with others. Be sure to pick one up so you don’t risk ruining your pump.
2. Aquaneat Large Double Sponge Filter
The Aquaneat Double Sponge is pretty cool because you get double the sponges. This model is best for bigger tanks, at least 20 gallons (75 liters ) and up to 55 gallons (208 liters).
The design on this filter is a bit different from the classic sponge filter. The lift tube attaches to the back wall of the aquarium and it branches out at the base to two separate sponges. It doesn’t require that you buy a separate air diffuser.
The lift tube telescopes, so it can go from 8-14 inches (20-35 centimeters).
Some users have complained that the suction cups that hold the lift tube wear out, but these can be replaced if needed.
3. Aquaneat Corner Sponge Filter
This has all the parts of a classic sponge filter, but instead of a round sponge, it’s wedge shaped so it fits in a corner.
Several users have complained that the base does not have enough weight to keep the filter from floating at times. So it may need to be buried in the gravel.
The strainer is too small for a regular airstone, so you’ll need to use one of the small, white air diffusers.
Also, you will get a big build up of gunk between the side of the tank and the sponge. It’s not a huge deal, it’s just something to be aware of when you go to clean it.
4. Hikari Bacto-Surge Foam Filter, XL (125 Gallon)
This Hikari filter is pretty darn huge. It’s a classic design sponge filter that isn’t supposed to need an added airstone.
Some folks do have issues with it floating up because the base doesn’t have enough weight. Make sure to squeeze all the air out of the sponge to help prevent this.
It’s listed as being able to handle up to a 125 gallon (473 liters), but I’m a little skeptical about that. But it would definitely be great for something like a 55 gallon (208 liter).
5. Upettools Ultra Quiet Sponge Filter
The Upettools filter is kind of like a combination between a sponge filter and a corner filter. Water flows through a ridged sponge and then passes through a chamber filled with ceramic biomedia (media included with purchase).
This gives you even more surface area for beneficial bacteria, and does not require that you add a diffuser.
It’s on the smaller side, only rated for up to 15 gallons (56 liters). There are dual and single sponge models so you have a few options to choose from.
Users comment on how quiet this unit is when it’s running.
6. Huijukon Sponge Filter
The Huijukon filter is similar in design to the Upettools filter, but has a much larger capacity. It’s rated for up to 60 gallons (227 liters).
There’s no need to add an airstone or diffuser and the lift tube telescopes so you can make it longer.
It has dual sponges as well as biomedia chambers (media not included). You can fill the chambers with the biomedia of your choice, or you can remove the chambers and run just the sponges.
I have to admit, I’m partial to the green color.
Choosing the Best Sponge Filter
So which one is the best?
Well, it’s hard to come up with a “best sponge filter” that works for everyone, so I’ll go with two.
I think the Hikari Bacto-Surge sponge filter is your best bet for a larger tank. It’s got the surface area you need to grow a good sized colony of beneficial bacteria.
For smaller tanks, I’d like the Upettools Ultra Quiet sponge filter. I like that you get the extra biomedia and that you can adjust the lift tube to go above the water line.
All in all, I highly recommend sponge filters, either on their own or to boost your existing filtration. They really add so much surface area for beneficial bacteria, they’re easy to set up and operate and they’re cheap.
What’s not to love?
FAQ: How to Clean a Sponge Filter
Cleaning a sponge filter is super easy.
- Siphon some water out of your tank into a large bucket.
- Remove the sponge filter and take it off the strainer.
- Then just squeeze the sponge in the old tank water several times to get out the gunk. You’ll be amazed how much yucky stuff will come out of a sponge, even a small one.
- Discard the water and put your sponge filter back together.
- Voila, you’re done!
Pro Tip: Always use dechlorinated water. The chlorine in tap water can kill the beneficial bacteria living in your sponge.
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Last update on 2019-10-21 / Affiliate links / Images from Amazon Product Advertising API