Canister filters are really just an external powerfilter that doesnt hang on the aquarium but sits on the floor or under the aquarium itself.
It can be used for mechanical, chemical, and/or biological filtration in saltwater aquarium systems. They are pretty versatile.
It can be used continuously, or added and run only when needed. It is self-contained and high pressure pump.
It draws water from the aquarium with an intake tube and returns it with an output tube. You can direct the output tube anywhere you like.
It can be directed to another filtration system, see undergravel filter page.
The filter contains compartments with different kinds of filter media. Activated carbon, filter sponges, filter floss, and ceramic bodies are some of the filter media.
This is another one of its advantages – it’s large media capacity. It has roomy media capacity. But of course, the number will vary from model to model.
Whatever the number might be, it is made to filter large amounts of water. I believe it is a great choice since they are made for enhanced performance and convenience.
The water is pumped over the media layers. These filters are definitely more expensive than others but provide outstanding efficiency.
They dont need to be cleaned all the time. Multiple filter media also allows bacteria to stay when the filter is cleaned about every three to four months.
If you plan to house not only fish but invertebrates and all kinds of corals, I would recommend getting a canister filter.
It can act as a stand alone filter, or be used in combination with other types of filtration.
Here are some examples for each category.
Mechanical Filtration
If you have an undergravel filter, can add a hang-on-tank canister filter to remove free floating debris from the water.
If you continue running a canister filter on this type of set up, it will contribute in the improvement of your water quality.
If you have a semi-reef system with fish and some live rock in it, you can install a canister filter inline to act as a “prefilter” to remove unwanted waste from your saltwater aquarium water before it goes through the actual biological filter.
This can also be done on full reef tanks with live rock and corals in them, but the debate about continually running mechanical filtration in this type of system is that such a set up filters out beneficial plankton life in the water that many marine organisms feed on.
For Chemical Filtration
If you need help in clearing up the water quality, they can place activated carbon in one of the media layers to help eliminate odors, medications or other contaminates in the water.
You can also use other types of absorbing products that are designed to remove nitrates, phosphates, silicates and other unwanted chemical elements or compounds.
For Biological Filtration
Many are designed for this use. Actually a lot of aquarists use them in this way. But I think this is not a good choice if you are to use it as your “main” source for biological filtration.
Its ok for smaller systems, but most do not have a chamber big enough to hold a sufficient amount of bio-media in them for larger ones.