Below is an overview of the four most popular types of aquarium filter for use in your freshwater fish tank.
There are three different types of filtration that you must consider for your fish tank. Chemical filtration helps to remove chemicals from the aquarium and is usually done with activated charcoal. Biological filtration uses beneficial bacteria, present in all aquariums, and the nitrogen cycle. Mechanical aquarium filters uses a physical barrier to remove particles from the water.
Aquarium Filter Type: In Tank Corner Filter
This type of aquarium filter is for use in small fish tanks only. It consists of a small plastic box with holes or slits in the sides, bottom, and lid. Inside there are two layers. Activated charcoal goes in the bottom and provides chemical filtration. Cotton or polyester batting, or filter material, goes on top of the charcoal. This provides mechanical filtration. A small external pump sucks the water through the bottom and out through the top.
This type of aquarium filter is inexpensive, acceptably efficient for smaller fish tanks, but difficult to maintain. Whenever the filter medium needs to be changed, the entire canister must be taken out of the tank, cleaned, and then replaced. This is disruptive to the aquarium.
Aquarium Filter Type: Under gravel Filter and Power Heads
The under gravel aquarium filter provides only biological filtration because it provides a place for the bacteria to grow. This type of filter consists of slotted plastic trays that sit on the bottom of your fish tank under the gravel.
Long, plastic tubes are attached to the under gravel filter and power heads are often used at the top. Power heads are pumps that suck the water up from under the under gravel filter and spray it out over the surface of the water.
Under gravel filters are the most ineffective. Debris such as fallen fish food can be sucked down through the gravel and remain in the water under the plastic trays. These aquarium filters should be used only with another type of filter.
Aquarium Filter Type: Hang on Tank Filter
The hang on tank (HOT) aquarium filter is the most popular for all size tanks. These filters are plastic boxes that hang on the back or side of the fish tank. A long tube goes into the aquarium and sucks water up into the filter. The water flows through a series of chemical and physical barriers and then cascades back into the tank. Some provide filter media on which bacterial colonies can grow as well.
This type of aquarium filter is very efficient and easy to clean. The filtration material is usually on small trays that can simply be pulled out and either washed or discarded when they grow dirty.
Aquarium Filter Type: Canister Filter
The canister filter is another external system. Tubes inside the aquarium suck the water out and run it through the canister. This type of aquarium filter has three levels of filtration: a filter medium on which bacteria can grow, a layer of chemical filtration such as activated charcoal, and a physical barrier as in the corner filter described above. They are usually more expensive than the other types of fish tank filters, but more efficient and easy to maintain.
