Sponge Filters: 10 Reasons Why They’re Awesome for Aquariums

Sponge filters are sometimes seen as filters for bowls and beginners – but nothing could be further from the truth!

A sponge filter with the right knowledge is a wonderful tool for any sort of aquarist.

They even have a number of advantages over the expensive, seemingly powerful hang on the back and canister filters that we so often use!

Let’s consider 10 reasons why sponge filters are a great choice for your aquarium!


Reason 1: Expense

Sponge filters have fallen out of favor in the fishkeeping world. While a trip to the aquarium store reveals several filters requiring different cartridges and media, you’re likely to only find a couple sponge filter varieties. Why is this?

Sponge filters aren’t as popular for fish stores because they are simply too inexpensive and generate little income. The setup is a simple sponge and some plastic housing.

And once you purchase the filter you aren’t coming back for charcoal media, bags, frames, electric pumps, and all of the other accessories needed to run other filters. These items all cost money and the belief that they are required keeps you returning frequently, paying more than you would for a simple sponge filter with every visit!

pet store isle

It makes much more economic sense to push the hang on the back and canister filters. Not that these don’t have a place; customizable media is excellent for treating specific imbalances in aquarium ecosystems.

But for a healthy aquarium with a moderate to low bioload a sponge filter is a great choice when considering expense to efficiency!

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Reason 2: Simplicity

Sponge filters are…Well, just a sponge with plastic housing of varying design. The most common style uses a strainer and lift tube with an attachment at the top for a silicone air line running from a pump.

As bubbles form within the strainer and lift tube and rise, they create a gentle current that pulls water through the sponge. The sponge at first provides purely mechanical filtration. Over time beneficial bacteria colonize the filter, providing biological filtration as the tank fully cycles.

The working concept is identical to both hang on the back and canister filters. The only components these filters provide is faster water flow and chemical filtration when using charcoal, zeolite, and other specialized media.

Biological and mechanical filtration are still much more important to a health aquarium, however.


Reason 3: Gentle Current

Sponge filters are the best filters for aquariums where you need to use an extremely gentle current. If you’re raising fish fry, Brine Shrimp, or other tiny aquatic organisms, any sort of powered filtration is going to suck them up and kill them.

By using a smaller air pump or using the regulators on either the pump or the filter itself you can provide ample mechanical and biological filtration without endangering your animals. The turnover rate is far slower than a canister of hang on the back style filter. But not necessarily less effective.

Frequent spawners like Livebearers also constantly lose fry to powerful filter intakes. Sponge filters are great choices for tanks where you never know if babies will arrive.


Reason 4: They Are Easily Repaired or Replaced When Damaged

Being so simple they are also difficult to damage because they are built with rigid components. Electric filter components like magnetic impellers eventually get gravel or rocks inside and need maintenance.

Canister filters require you to detach hoses and pipes, undo the locks, and sometimes bring out the manual for specialized issues and organizing your compartments.

Sponge filters are as simple as they come. The majority of problems will be along the lines of cracked plastic and decaying sponges, both of which are easy to identify and replace. If less tech savvy folks are maintaining an aquarium or bowl a sponge filter is by far the best choice.


Reason 5: Sponge Filters Are Very Quiet

How quiet the sponge filter is depends entirely on the pump that drives it. And with the rubberized seals and mechanics of modern day brands these pumps can be quiet enough to avoid disturbing even the lightest of sleepers.

Sponge filters do cause surface agitation but not nearly as much as other filter styles, which can sound like miniature waterfalls. Many people find this effect relaxing. But sometimes silence is better than background noise.

And despite their reduced capacity for surface agitation sponge filters provide plenty of gas exchange thanks to the constant flow of air bubbles. Both oxygen and carbon dioxide can be transferred in meaningful enough amounts for both fish and plants to thrive.


Reason 6: Sponge Filters are Great Pre-Filters

If you are still fully committed to running a hang on the back or canister filter, then consider adding a sponge filter to the mix! Instead of running a separate unit a simple block of foam over the intake will give you most of the benefits of a separate sponge filter while allowing you to still get good chemical filtration.

A sponge block over the intake also helps preserve small fish and shrimp from the suction power of larger canister filters. Over time the block will be colonized by beneficial bacteria in much the same way as a dedicated sponge filter would. However the smaller surface area means that the main filter is doing more biological filtration work.


Reason 7: Sponge Filters Partner Well with Other Filter Types

You can never really overdo mechanical and biological filtration. Extra surface area is always in demand and beneficial for aquariums. They do live free floating in the water column and attached to rocks and plants. Even gravel and sand with their high surface area provide places for these microorganisms to thrive.

However if there is a spot where a sponge filter can be tucked away such as behind a piece of driftwood or a corner there’s no reason not to add extra capacity to your filtration. This is especially useful if your tank is on the overcrowded side of things. Extra bacteria will break down ammonia and leftover food that much faster!


Reason 8: They Can Be Used With Any Aquarium Type

Freshwater, saltwater, paludarium, planted aquarium, shrimp-only, brackish…You can use the same brand of sponge filter for each one of these aquariums! The more fish you have and the larger the aquarium, the larger the sponge filter you will use.


Reason 9: Sponge Filters Continue To Work During Power Outages

When the worst happens during a winter storm and the power goes out that spells the end for water turnover. Your aquarium is officially separated from your canister and hang on the back filter and the bacteria within are deprived of oxygen.

As aerobic organisms they will eventually suffocate and die, depending on how long they go without. This can destabilize your cycled aquarium and cause deaths even if the loss of heat doesn’t kill your fish.

Sponge filters remain immersed in the aquarium and are not only revitalized but actively breaking down waste throughout the outage! While bacteria may be affected by the lack of current they won’t die off entirely no matter how long it lasts.

The mechanical filtration aspect no longer continues however biological filtration does not entirely stop and helps keep fish healthy.


Reason 10: They Are The Fastest Filters to Clean

Sponge filters are quick and easy to clean because the dirt is part of the appeal! Cleaning a sponge filter is a matter of removing just enough material without endangering your bacterial colony. We don’t want a pristine sponge; we want the free flow of water throughout the media.

Freshwater aquarium sponge filter

When running a single sponge in an aquarium with a moderate bioload we may have to clean it every 3 weeks to 1 month. Many aquarists think to remove the sponge, squeeze it several times under running tap water and then replace it, as if sanitizing a cleaning sponge.

This is the absolute worst thing to do! You’ve essentially stripped your bacterial colony and then partially sterilized the sponge with chlorinated water. Your aquarium may even suffer an ammonia spike as the disrupted colony can now no longer process fish waste as effectively.

Instead you should use a small bucket or tray of aquarium water to clean your sponge. Brush off any surface debris that’s still clinging to the outer layers and then give your sponge filter one or two squeezes to remove the worst of the attached gunk.

Remember that the gunk is a mixture of partially decomposed organics and beneficial bacteria. We want some gunk to remain on our sponge because that’s where the biological activity is happening! We just don’t want so much gunk that it impedes the flow of water through the sponge.

Once you’ve removed enough for water to flow mostly unimpeded, re-attach your sponge to the plastic housing or life tube and you’re done! No researching the right chemical media, finding frames to fit filter bags, or calling pet stores to see who even carries that brand anymore…Sponge filters are the best friends of both beginner and advanced aquarists alike!

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