Fish Tanks

How to Clean and Maintain an Aquarium Filter

how to clean an aquarium filter

Aside from the glass walls of a fish tank, the aquarium filter is the most important aspect to the safety of any fish living in any artificial body of water. Learning how to clean an aquarium filter is essential to the life and long term well being of your aquarium fish. You are looking after a delicate mini ecosystem.

The filter should make maintaining a fish tank a relatively simple task, as it works around the clock to keep water clean, purified and hosts beneficial bacteria needed to ensure good water quality.

Unfortunately, filters commonly get clogged, and need regular maintenance in order to stay running smoothly.

We’ll also talk in depth about how beneficial bacteria in filter medium is part of the filter’s ability to keep a tank clean. It’s not just about removing dirt and particles from water. This is essential knowledge for any fish keeper.

Clean out an aquarium filter

When to clean an aquarium filter

There are many reasons why we need to clean an aquarium filter, but they’re not always obvious.

The chances are that you probably already have some kind of system or schedule in place when it comes to cleaning your aquarium. In addition to performing weekly water changes, you probably also perform a larger water change once a month and replace your filter media. But when do you clean your tank filter? Do you clean it at all? If you want to keep your tank clean and running properly, you need to include your aquarium filter in your routine cleaning schedule.

Cleaning your filter will often depend on three main things:

  • The type of filter you have
  • How often you do a water change
  • If the filter is slowing down

Other factors come into play here, these are influences such as how many fish you have, often referred to as an aquarium’s ‘stock’. The best way to monitor when you need to change or clean a filter is based on how the outflow of the filter is functioning. A slow output usually indicates clogging, and very rarely a mechanical issue. The other obvious way to detect filter efficiency is just to judge the dirtiness of the tank. If your filter contains fine filters, often seen in canister filters as the final polishing filter, then these will slow down the out put much quicker.

Cleaning your filter isn’t a one size fits all process. You have to clean the filter depending on the type of filter installed. Obviously, some filters come with a instruction booklet on this, but they don’t always take into account biological factors. For example, if you’re reusing filter material, you must clean it using purified and treated (fish safe) water.

How to clean your aquarium filter

Aquarium filters work in more ways than simply collecting dirt from the tank. Beneficial bacteria (a lot like those good gut drinks we’re always being sold) live in the filter medium that actually keep water quality stable and safe for fish. They attempt to mimic the natural ecosystem filter found in dense plantation and substrate where fish naturally live. Cleaning the filter is therefore a delicate process. Any sudden changes in water quality can cause your fish to go into shock.

There are several things you need to keep in mind when you then clean or replace parts of a filter. The first is that you never replace all the filter medium in one go. Usually, I never replace mine until they have become impossible to clean. This applies to all types of filtration media, from sponges to medium like Fluval’s BioMax media. If you replace the filter medium all in one go, you loose ALL of the beneficial bacteria.

When you clean a filter, instead of replacing it, you have to be careful not to kill the bacteria that are living in the filters. That means not using chlorinated water to rinse them in. Cold water can also have the same effect. The best thing to do is take a bucket of aquarium water out and rinse the filter medium in that. This preserves a lot of the bacteria and simply removes the big dirt buildups that were clogging the filter.

How to clean an aquarium filter depends on the type of filter medium have.  Let’s get stuck into it:

  • Filter sponge.

This is the bread and butter of most filters. In a lot of cheaper or smaller filters this is the only type of medium available. This type of coarse filter is easily cleaned, and should rarely be replaced. The filter will still contain beneficial amounts of bacteria even after rinsed in aquarium water. It will often be paired with at least one other sponge filter, so my suggestion is to clean one at a time. Definitely do not replace more than one!

  • Filter floss.

Also known as a polishing filter, it’s meant to be the last filter water will flow through before returning to the tank. It’s not to prevent clogging in the rest of the filter, the main sponge takes care of the ‘big bits’, it simply collects the tiniest particles of dirt that weren’t caught by the main filter. Usually you’ll have a very clean tank when you use one of these. It usually clogs up fast and is difficult to clean because the sponge is so fine. I take it out once a month and wash it. It’s probably not frequent enough, because it’s always filthy. These need replacing or cleaning every 2 to 4 weeks. If you’re unable to clean it, you should just replace the polishing filter.

  • Chemical Filtration

Chemical Filters are filters than contain a special type of filter medium that clean the tank in an unconventional way. These are most commonly carbon filters, a lot like a water filter at home. They work by removing dyes and heavy metals. However, after prolonged use, they can actually release the dyes and heavy metal back into the water. It’s best to replace the filter entirely, every 1 to 2 months.

  • Biological filters

These filters are full of good bacteria important for aquarium filtration. Cleaning it is easy, you simple gentle submerge it in clean (and treated) water. Do not rinse this throughly, as you’ll wash off all the bacteria. Most common in canister filters, they provide a high cylindrical surface area and thus are a hub of bacteria.

Usually, I will only replace a biological filter if the parts are crumbling or so filthy if will affect the speed of the pump.

This is a great video from RC aquatics too:

How often do you clean your aquarium filter? Let us know in the comments!


About the author

Authority Aquarium Staff

Authority Aquarium Staff writers are experts and aquarium enthusiasts, our in-house marine biologist fact checks all our content and reviews to bring you the best advice for your aquarium health.

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