Filtration - Part 3 - The Corner Filter and the Canister Filter
As a beginner aquarium keeper, one of the first types of mechanical filter that you encounter is probably the trusty old corner filter. The corner filter is inexpensive to purchase compared to many other types of mechanical filters, and also easy to install. The basic corner filter will be a plastic container filled with a filter medium, e.g. foam or floss. An air pump will be used to force water through the filter, thus trapping larger debris. A corner filter will therefore often also function as an aerator for the aquarium.
Be careful when you clean your filter medium and never use hot water or detergents. When you have performed a water change, the discarded water can be used to wash the filter medium since it will have the right temperature, pH etc. The reason why you should handle your filter media so carefully is that it is a great home for beneficial bacteria. If colonies of nitrifying bacteria colonies the filter media, they will perform biological filtration and make it much easier for you to keep the water quality up in your aquarium. Hot water, detergents etc will however kill the bacteria and must therefore be avoided. If you need to replace the filter media, you should ideally leave a part of the old media in the canister filter. This way, the old bacteria can colonies the new filter media.
A downside with the corner filter is that many designs produce a lot of noise. You can of course find good looking corner filters, but a majority of the corner filters are actually quite ugly. If you have messy eaters, the corner filter will be rapidly clogged and require frequent cleaning. The corner filter can also be insufficient for aquariums that require more vigorous filtration.
Canister filter
For aquarium keepers that keep messy eaters or have large aquariums, the basic corner filter is often not enough to keep the water quality up. If you find your self in this situation, you might want to consider the canister filter. This filter is an external filter that is hung outside the aquarium or placed under the aquarium. Today you can also find canister filters that are located inside aquariums (submersible canister filters), but they are much less common than external canister filters. The inside of this filter will typically contain a micron filter cartridge, glass wool or similar types of filter media. Waster is then pumped through the canister filter, and larger debris is caught in the media. This makes the canister filter quite similar to the basic corner filter, only much larger and more powerful. You can also add a wet-dry wheel to your filter to promote biological filtration.
Just like with the corner filter, you must clean your canister filter frequently to prevent clogging. If the caught debris is left too long in this filter, they will start decomposing and can pollute the water. A negative aspect of the canister filter is of course that it requires a lot of space. A submersible canister filter will take up a lot of space and look ugly inside the aquarium, while an external canister filter will take up a lot of space and look ugly somewhere outside the aquarium. Careful planning can be the solution here; you can for instance hide the external canister filter in a piece of aquarium furniture. Just keep in mind that it must be easy to access the canister filter, since it requires frequent cleaning. Never use soap or hot water when cleaning your filter.
