These days there are many Aquarium Filters to choose ranging from the classic UGF (Under-gravel Filter) to today's Power Filter.
Here is a list and information about types of Aquarium Filters.
Power Filters is one of the most popular filters for an aquarium. It can be a hang on filter or it can be an internal filter. Power Filter works by pulling water from the aquarium and water is pushed through a sponge or filter pad and pushed through carbon and/or bio media. Power Filters are powerful and do a good job on filtering the aquarium water but they do not do a good on aquariums over 100 gallons of water. But Power Filters will do a good job in an aquarium with 1-100 gallons of water.
Marineland(R) is the first and only aquarium company to produced the Bio Wheel Filter. There is two models of the Bio Wheel Filter and one is the Penguin(R) and the Emperor(R). So which one to choose? OK Let's start with the Emperor (R) first. The Emperor(R) delivers a more powerful flow than the penguin and it delivers a bigger capacity and it delivers a very efficient flow to your aquarium that means the aquarium inhabitants will get more oxygen with this filter. Now the Penguin(R). The Penguin(R) delivers an adequate flow but not as powerful as the Emperor(R) will provide. But the Penguin(R) noise reducing design so its great for hobbyist that do not like noise. A Bio Wheel Filter is a hang on power filter with a Bio Wheel in it. Bio Wheel Filters work similar to the power filter which pulls water from the aquarium and passes through a Bio Wheel. The Bio Wheel will grown a lot of bacteria good for overpopulated tanks. Bio Wheel Filters provides a three stage filtration: Mechanical, Chemical and Biological. Same as Power Filters they do not do well in a tank over 100 gallons of water.
Canister Filters deliver an efficient flow and filtration. Canister Filters work by pulling water from a hose to the Canister which is placed outside the aquarium and passing through floss, carbon, and bio media. Canister Filter provides a good filtration for 25-400 Gallon Aquariums. Canister Filter has a 3 stage filtration: Mechanical, Chemical, Biological. But one con about these canister filters is that cleaning takes a lot of time and putting back together takes a lot of time. Another con is that Canister Filters are prone to leaks but many newer Canister Filter are now not prone to leaks.
Sponge Filters is powered by an air pump and it is placed inside the aquarium. Sponge Filters work by pulling water through the sponge and the is pumped back into the aquarium by column. Sponge Filters provide a good filtration on mechanical and biological. When water flows through the sponge large amount of bacteria will grow. When cleaning the sponge just remove the bottom (depending on your sponge filter) and take the sponge out and rinse it with the water you removed from the aquarium. These filters will provide a good filtration for breeding tanks but not a good filtration for tanks with full grown fish.
A Sump Filter is an external tank ranging from 20-70+ Gallons. Sump Filters work by pulling the Aquarium Water into the external tank passing through floss (on some sump filters), carbon (on some sump filters) and they usually through Bio Balls, Bio Wheel or if it is a DIY dish scrubbers. They usually provide good benefits on Biological Filtration.
Under-gravel Filter (UGF)
Under-gravel Filter have been around the Aquarium hobby for a long time. Under-gravel Filters is a plate that sits under the gravel which is powered by an air pump or a powerhead. Under-gravel Filter works by drawing the water and putting debris under the filter plate. Biological Filtration will start under the gravel. If these filter aren't maintain well there could be serious problems in your tank. Aquarium World does not recommend hobbyist to use Under-gravel Filters. There have been a lot of controversies about the Under-gravel Filter. Click here for a Google search about the Under-gravel Filter Controversy.
Box/Corner Filters have been for a long time too. Box Filter are placed on the corner of the aquarium and they are usually fitted with filter floss, carbon and sometimes Bio Media.. The Box/Corner filter is a very low tech filter which is powered by an air pump. They work by pulling water from the aquarium and passing through the filter material and then pumped back into the aquarium. They provide good filtration for mechanical, chemical, and biological filtration. Box/Corner do a good job in smaller tanks but in bigger tanks they do not work well.