Does A Canister Filter Have To Be Below The Tank? (And What Media To Use)

A canister filter works hard to ensure your aquarium’s water is as clean as possible and when you have a good one, it can make clean up a lot easier but if you haven’t used one before, it can be difficult to know where to place it. Get this wrong, and the filter will need to work harder than it should and could even cease to perform to the level you expect. When this happens, the water loses clarity and is just not as hygienic as your fish need. Because everyone needs to know as much as possible before purchasing one, the following article is designed to help.

So, Where To Place A Canister Filter?

To answer the common question, a canister filter needs to be placed below the water for it to work. This is because it relies on this position to prime the water and to help push it through and if it is level with the water, it does no siphon in the same way and will have to force it along. For some products, this is too much and can cause it to break.

Where To Start?

When you open the box there are lots of different parts to connect so the best place to start is with the instruction manual. Get to know the different components so you can identify any issues later on. You should have everything from hoses and clips to the foam inserts, and media trays and baskets among other items. This is also where you can see if anything is missing so you aren’t wondering if you have done something wrong when it comes to set up.

What Media To Use In A Canister Filter

This is the all-important part of what makes a canister filter effective. The different media trays can vary, all the reputable products we have reviewed tend to have at least three.  Before purchasing there are certain considerations such as the environment they will be used in. A saltwater aquarium will mean different needs should be met as the plant life will be different.


A lot of people will say this is the most important type which is why all canister filters tend to have them. Placed first in the line, they trap large debris and often come in the form of pads. When cleaned properly they can be used time and again so expect them to last a long time. Because of the way they are made, they do a good job of collecting debris without disrupting the flow of the water unless they get clogged. This is why you need to stay on top of maintenance.


This helps to maintain healthy bacteria levels that are optimal for fish life, keeping a portion of the good and are available in different varieties. Plastic bio-balls are some of the most commonly used and are ideal for large filters. Most of the time they do not require replacing as long as they are well maintained. You only need to remove debris as a proper wash can remove some of the good bacteria.

Other types of biological filters include rock and string among others.


Mostly in the form of carbon pads, they might not be so much like the chemical type of filter you had in mind. Still, this is the filter part that helps to stop bad odor from ruining your enjoyment of the aquarium. The carbon has other uses including improving the clarity of the water and stop the harmful chemicals you don’t want in the water from staying there.

Once they turn dark you know it is time to replace them but it is important to find the right type for your tank as some can remove useful chemicals as well as the bad types.

Why Buy A Canister Filter?

Because of its position below the tank, they are easy to clean. Doing so will not disrupt the fish in a way that other filters can so your fish can live without. the stress of such interruptions. A lot of people like these filters because they can be kept out of the way. When they are not in plain view and stored below, these units leave you with uninterrupted views of your fish.

It is better to find a product with an adjustable flow rate so you can move it between tanks should you purchase another. If you purchase slow-moving fish, they in particular will benefit from this feature because you can turn down the flow rate to make life more comfortable for them. Known for their quiet operation, a canister filter is a good option for anyone, and since a lot of the filter options will last a long time when looked after properly, they are low maintenance.

Canister Filter Vs Power Filter

This is one of the main considerations when buying and stocking an aquarium and both can do a good job of keeping the water clean. Ironically in terms of power, it is the canister filter that is capable of generating more. However, when it comes to installation and setting up, they do take longer, but that is because there are more intricate parts to connect.

Still, a canister filter is known for being efficient and tends to clean the tanks more efficiently than a power filter. A lot depends on the model of course but because of the way they run, there is no risk of loss of fish or water which is one of the potential downsides of a power filter through evaporation.

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