Sponge Filter for Aquarium – All You Need to Know

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There’s no doubt that external filtration is necessary to preserve an aquatic system’s stability and safety. Fish don’t need any type of filtration in the wild, because Mother Nature takes up on that role.

Open aquatic ecosystems have a natural filtration mechanism that dilutes harmful chemicals and stabilizes water conditions. These effects are often the direct result of water movement and bacterial activity.

The situation is vastly different in a closed ecosystem like an aquarium, where harmful chemicals like nitrites, ammonia, and, to a lesser degree, nitrates are.

You require a combination of external filtration and some good maintenance work to preserve the system’s stability.

Today, we will discuss the former, more precisely, about a specific type of filter: sponge filters.

What is a Sponge Filter?

Sponge filters are normal filtration systems that rely on sponges for enhanced mechanical filtration.

This type of filtration is more specialized, as it is optimal in certain scenarios and suboptimal in others.

The situations that require the presence of a sponge filter include:

  • Fry tanks – Fish fry can get quite small, depending on the fish species in question. It’s not uncommon for the fry to get sucked into the filtration system if the filter isn’t secure. The sponge filter is great in this sense because it prevents the fry from getting in.
  • Low water movement – Every aquatic setup requires a good filtration system, but filters create quite a lot of water movement. Especially the more powerful ones meant for larger aquariums. The sponge filter provides great mechanical filtration while keeping water movement to a minimum. This is great for more sensitive fish species that like still waters, like bettas, among others.
  • Great for sensitive fish – Some fish species require pristine waters with as little floating matter as possible. The sponge filter is one of the most effective mechanical filters available, as it traps even the smallest floating particles. This allows you to preserve the water quality and keep your fish in good physical and mental health over the years.

It also doesn’t hurt that sponge filters are considerably simpler and easier to install and operate than more advanced filtration systems like HOB and canister units.

How to Set Up a Sponge Filter?

If your sponge filter isn’t assembled at arrival (and most of them aren’t), you need to do the work yourself.

Fortunately, it should be a walk in the park with the proper guidance.

Here’s what you should do:

  • Get adequate components – Not all sponge filters come with the same components. For some, you need to get additional pieces to personalize the filter, depending on your setting. The components you need include the filter itself, an air pump, the airline tubbing, and the airflow valve, in case you have an adjustable filtration system.
  • Assemble the filter – The operation should be easy-to-follow, as you only need to follow the assembly instructions that arrive with the package. Sponge filters are simple, so the assembly process won’t take much time. There’s also little-to-no room for mistakes, primarily due to the system’s simplicity. For a quick guide, you have a weighted base extender keeping the filter from touching the substrate, 1 or 2 plastic tubes with side holes that go inside the sponge(s), and an uplift tube for airflow control.
  • Attach the airflow hose – One of the hose’s ends attaches to the system via a small extrusion. The other end connects to the air pump.
  • Connect the airflow valve – This one is optional in case you need an additional degree of control. The airflow valve goes into the section between the air pump and the main filtration system and helps control the airflow. Place the vale itself closer to the air pump for ease of use.
  • Submerge the filter – After mounting the sponge(s), which is standard work, you can now immerse the filter into the water. Keep it submerged by force for a minute or 2 until the filter gets enough water to sink. Otherwise, the filter will simply float, despite the weighted base.

All you have left after all this is to verify the filter’s functioning and tweak it according to your needs.

How Does a Sponge Filter Work?

The working mechanism is rather straightforward. The sponge filter relies on the air pump to create upward pressure, forcing the water through the filtration mechanism.

The water will traverse the sponges, which will trap any particle floating nearby.

Because sponges are so dense, they will trap even the smallest particles, making sponge filters some of the most reliable mechanical cleaners you can get.

How Long Does it Take for a Sponge Filter to Cycle?

The sponge filter should take approximately 4-6 weeks to cycle properly. You should monitor water parameters and supervise the cycling process daily because the cycle time varies drastically depending on several factors.

These include the tank’s size, the ammonia source you’re using, whether you have plants or fish in the tank, the filter’s type, size, power, etc.

How to Clean a Sponge Filter?

Fortunately, the filter cleaning process is simple, as you only need to clean the sponge itself for the most part.

However, there’s one way to get it right and a ton of ways to screw it up.

You should always:

  • Clean the sponge filter with aquarium water – Don’t use tap water because it contains chlorine. The aquarium water is perfect for the job as it doesn’t contain any harmful chemicals and protects the colonies of bacteria inhabiting the filter.
  • Clean the filter just enough – Don’t be too thorough about it. Some surface cleaning should be enough unless your filter is excessively dirty and clogged. The goal is to remove visible algae deposits, detritus, mineralized dirt, and plant matter that may accumulate with time. Overcleaning the filter will disturb the algae population, eventually affecting the entire system’s stability.
  • Skip cleaning chemicals – Don’t use soap, bleach, vinegar, or any other cleaning chemical. These will disinfect the filter, which will eradicate the filter’s bacterial population. These chemicals can also linger inside the filtration mechanism and hitchhike their way to the main tank, causing a chemical disaster.
  • Stick to a steady maintenance routine – You don’t want to clean your filter too rarely, as this increases the risk of clogging and decreases the filter’s effectiveness. But you don’t want to clean it too often either, as doing so will impact the bacterial population severely. The ideal filter maintenance and cleaning timeframe are 30 days unless the situation demands otherwise. You can go for a quick cleaning session even before that if you notice a decrease in air bubbles, suggesting that the sponge may have been overwhelmed with detritus.

An interesting point here: always be smart about replacing your sponges. Sponges aren’t everlasting.

They generally have a lifespan of 4-6 months, depending on the filter’s size, the tank’s size, the layout, and what type of fish you have, etc.

Overfeeding your fish and keeping messy creatures like goldfish may overburden the fish sooner, requiring more frequent replacement.

But this isn’t what I wanted to talk about, but the actual replacement process.

You can’t just purchase a new sponge, remove the old one, install the new one and call it a day. That’s because the new sponge is practically sterile and contains no bacterial deposits.

Replacing your sponges like that will lead to an environmental catastrophe, as the lack of denitrifying bacteria will quickly lead to ammonia and nitrite overdoses in your tank water.

Instead, you should clean the old sponge, cut it in 2, and use one of the halves in conjunction with the new sponges.

Keep the filter running with this sponge setup for approximately 4-6 weeks, enough for the bacteria to migrate from old to new sponges.

Sponge Filter vs. Other Filters

Sponge Filter vs. HOB (Hang-On-Back) Filter

On one hand, sponge filters are better for chemical filtration. This is due to the sponge’s improved density, allowing the material to stop even the smallest specs of matter floating in the tank.

It’s also a plus that sponge filters are highly customizable, as you can use different sponges for different jobs. Coarser sponges offer improved water flow, while finer ones keep water movement to a minimum and filter smaller particles.

HOB filters aren’t as good in the mechanical filtration department, but they also offer a steady flow rate and ensure decent chemical filtration.

The problem with HOB filters is that they are very much circumstantial. They can clog a lot faster than sponge filters and require frequent maintenance, especially when used in more demanding environments.

Sponge Filter vs. Canister Filter

I would say that the canister filter towers over the sponge filter in terms of overall filtration effectiveness and flexibility.

Canister filters offer mechanical, biological, and chemical filtration, making them ideal for most aquatic setups.

The only problems worth mentioning are:

  • The difficulty of maintenanceCanister filters are notoriously tricky to disassemble and maintain, which is why more experienced aquarists often use them with more patience and dexterity than your average hobbyist.
  • The circumstantial usefulness – You can’t use canister filters for very small tanks that would benefit more from a smaller piece like a sponge filter.

Sponge Filter vs. Sump Filter

Sump filters are more useful for marine tanks and function as an extension of the aquarium itself.

They are generally massive and offer a complex filtration system aiming to:

  • Significantly improve water volume
  • Drastically increase water agitation for improved gas exchange
  • Store tank equipment out of sight
  • Boost water flow

Naturally, sump filters are extremely circumstantial. They are notoriously difficult to set up and maintain, take up a lot of space, and produce elevated evaporation rates.

They are also expensive, so they’re only fitting for larger ecosystems, mainly reef-based setups in need of strict water parameters.

There’s really no competition between sponge filters and sump filters because neither can replace the other due to the sump filter’s specialized functioning.

In essence, the type of filter you should use depends on the setup you’re using it for. Some ecosystems could very well thrive on a sponge filtration system, while others require different equipment.

When You Should Not Use a Sponge Filter?

While sponge filters are great as a whole, they are sometimes unfit for the job.

Here are some specific situations where you would be better off skipping the sponge filter in favor of a different filtration system:

  • In overcrowded or specific setupsOvercrowded tanks tend to produce a lot of fish waste and food residues. These can easily overburden the filtration mechanism, causing the filter to clog frequently. Some ecosystems can clog the sponge-based filtration system in a matter of days, and you don’t want that headache. Sponge filters are also unfit for ecosystems housing substrate diggers and excessively messy fish like cichlids, goldfish, and pufferfish.
  • In excessively large ecosystems – You can’t rely on sponge filters for vast aquarium setups that require more than one filtration system. A canister filter will be more fitting for those situations.
  • In systems where chemical filtration is necessary – Sponge filters don’t offer chemical filtration, so you cannot use them in ecosystems where chemical filtration is a necessity.

The good part is that you can use sponge filters to complement other filtration systems in case the sponge filter alone is unfit for the job.

You can always use the extra mechanical filtration precision of the sponge filter.


Sponge filters aren’t exactly versatile, but they are resilient and do a lot of precision work. These systems are great for small and medium setups that require intense mechanical filtration.

They are cheap, easy to maintain, and great for easy-going fish communities with a decent fish presence and activity.

Just make sure you clean the sponges regularly, supervise the filter’s functioning, and replace the sponges once they reach their expiration date.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.

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