A good filter is probably the most important piece of equipment you can add to your aquarium. Aquarium filters usually provide biological, chemical or mechanical filtration. You might want to get a filter that provides all three kinds of filtration in one, as this will make your tank easier to maintain.
Your fish will be healthier as well. A biological filter will reduce the toxicity of the tank, a mechanical filter will keep the water clear and a chemical filter will remove dissolved waste in the water and prevent the water in your tank from becoming yellow.
Power filters are one of the most commonly used filter types. These filters hang off the back of the aquarium. Power filters are perfect for smaller aquariums, since they do not take up valuable space inside the tank. They are convenient and easy to maintain and can provide both mechanical and chemical filtration. Power filters are inexpensive and easy to setup. You may want to use this filter along with a bio-wheel or a sponge to provide biological filtration.
Canister filters are ideal for medium to large tanks. They provide a combination of biological, chemical and mechanical filtration. They force water through media that most debris is unable to pass through and this allows for great mechanical filtration. You may want to purchase ceramic rings and sponges to help with biological filtration. You may also want to purchase carbons or resins for chemical filtration. Canister filters are a bit more difficult to maintain than some of the other filter types, because you will have to reach in the tank and pull out the filter to change it.
A wet/dry filter works by making water slowly dribble down over the filter material, allowing the water to receive as much air as possible. For biological filtration, the filter may use bio-wheels or bio-balls as media. For chemical filtration, it may use resins or carbons. For mechanical filtration, it may use a sponge. This filter will clog easily. To prevent this from happening so quickly, you may want to use a pre-filter.
A fluidized filter is a highly effective biological filter, but does not provide chemical or mechanical filtration. Fluidized filters pump water up through a small, fine media, such as sand, to provide enough surface area for bacteria to dwell on. They are very easy to maintain and are great filters to use in combination with another filter, especially in larger aquariums.
Sponge filters work by forcing water through a tube from an air pump, which then allows for bacteria to grow and provide biological filtration. The bacteria help to maintain the quality of the water. Sponge filters also provide mechanical filtration, but can clog up easily. You can quickly unclog them by squeezing the sponge out while holding it under chlorinated water to kill the bacteria. Sponge filters are perfect if you have baby fish in the tank, as they won’t get sucked into the air pump. These filters are very easy to maintain since you do not have to clean them.
Finally, remember that although filters help to maintain the quality of the water in your aquarium, you will still need to clean the tank and replace some of the water regularly. Also, you should be aware that different aquarium setups do better with certain filters. Talk to your local pet store professional about which filter is right for your tank.