What media to use in a canister filter?

If you are starting out in the aquarium hobby or want to switch from one type aquarium to the other you may be curious about how to use your canister filter. Different media in your cansiter filter can affect the environment of an aquarium in different ways, this is especially true when it comes to salt and freshwater environments.

In this article, you will learn about the different types of media for canister filters and what they are used for. We will also tell you the do’s and don’ts of using media in common types of aquariums. Keep reading below to learn more about the media that helps keep your water clean.

The Different Types of Canister Filter Media

There are three main types of media to learn about. These three are Chemical, Biological, and mechanical. They all have their different place in cleaning your water and their own personal properties to learn about in the proper order they should be placed in your filter.


Mechanical media is arguably the most important part of your canister filters. This media protects the chemical and biological media from becoming clogged by large debris Mechanical media always goes in the canister first and should before the other types in your filter.

Mechanical media is generally reusable as long as you clean it well. One of the most popular types of this media is pads. Pads are porous and easily catch debris the filter drags in. Pads can even be used to help control the water intake of the filter and control water flow.

Filter floss is also a type of media from the olden days of the hobby. This media is made from materials like wool and can substitute the need for a chemical layer. This media does well at capturing debri without disrupting the flow of water.

You must take care of your mechanical filter. These filters can become so clogged that they will greatly reduce the filters pull. If left clogged a mechanical filter can even do long-term damage to your aquarium and stain your canister filter.


When you think chemical media you probably picture something along the lines of a chemical gel you add to the filter. While this is partly true, one of the most common chemical methods you see used is carbon pads This media does a wonderful job of removing odors from the aquarium.

Carbon is also can absorb harmful chemicals while making the water clearer. There are also other types of media like poly-filters. These filters help by clearing the water and even turning a dark color to let you know they have exhausted themselves or what contaminants are in the water.

If you feel like your water has phosphates in it then Granular Ferric Oxide filters can help clear them out. This material can also clear up major algae growth that occurs in freshwater environments With this media you will need to test for phosphates to determine if it’s used up.

The downside with chemical media is that they have the potential to remove helpful nutrients from the tank. Carbon can especially be a culprit for removing some of the elements your aquarium needs to grow. Be sure to heavily research any chemical media before using it.


Biological media is made to be used for creating a home for bacteria colonies in the tank. Just like with most natural environment, your tank will need healthy bacteria to properly function. By putting in biological media and properly taking care of it your tank will stay balanced.

Biological media comes in a few different forms to choose from. Rock like bio media can fit in the small spaces of your canister. This type of media is commonly made from lava rocks and are easy to find. Another common type of bio media are plastic bio balls.

Bio balls are perfect for larger filters and if properly taken care of, won’t need to be replaced. These are ideal for nitrifying bacteria to live on. Next is the cell pore media, that are even made to fit specific filters. This media offers the most surface areas out of the biological media

Lastly, there is string media. This media can work well to divide your canister filter and even assists with mechanical filtering. With biological media be sure to only clean out debris that have become stuck in the filer Never wash or deep clean a biofilter as it will kill or remove the bacteria.

What to Think About When Choosing Media

When it comes to picking the best media for your aquarium there are a few players involved. First, how much water flow do you need in your aquarium? If you have an aquarium with large fish you will need a media porous enough to still give you a high flow.

If you’re trying to grow plants or have a reef aquarium then you may want to stay away from some chemical filters like carbon. These filters can kill the nutrients needed to help your reef grow properly. If you work a lot you also may want to look into filter media that requires less maintenance

Each media type and the amount of the media you use in some cases will influence the bacteria and growth of your environment. You need to look up the needs for each fish or plant in your aquarium and research there needs. This can help you determine which media will provide the best bacteria growth, water flow, and the type of cleaning that particular aquarium will need.

Picking Your Canister Filter Media

Now that you have the rundown for your aquarium and understand the media types and their impact you can begin to understand your aquariums needs. Look at the size of your fish and decide if you want live plants in your aquarium. This will give you a good place to start.

Once that’s decided, do you want a salt or freshwater environment. If it’s salt and you want tropical fish then you will need to look into what media will best promote the growth of coral. The media choice for your canister filter is all about understanding the habitat you want to create based on the inhabitants of your tank.

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