Generally speaking, there are 3 types of filtration: biological, chemical and mechanical.
1. Biological filtration - Biological filtration is used in the nitrogen cycle (converting fish waste and food debris which first turns into ammonia by bacteria and then into nitrites and nitrates), and is necessary for the health of your fish.
2. Chemical Filtration - Chemical filtration involves removing any and all compounds that have already dissolved into the water in your aquarium. Again, this is essential to keep your Betta happy and healthy.
3. Mechanical Filtration - Mechanical filtration involves filtering out the particulate debris in your fish tank. When the aquarium water gets cloudy, mechanical filters allow plastic foam, fiber floss or even sponges to catch the debris in the water.
With the popularity of aquariums, there are many types of filtration systems available.
Corner Box Filter
One of the most tried and true and oldest of filters is the Corner Box Filter. This specific filter rests on the gravel or substrate in the “corner” of the tank. It has a single airstone (a porous diffuser that air is forced through that releases oxygen bubbles into the aquarium), which is connected to a single pump that is used to push the water through charcoal and floss contained in the box.
Another type of filter is the Power Filter. Coming in a variety of different sizes, most times they hold either 1 or 2 openings that hold pads made of fiber which contain a bit of activated carbon. These pads normally hang on the back of the fish tank while a pump pushes the water through the pads which collects the debris, then pushes the water back out into the tank.
Once the most common and the standard in fish tank filters, the Undergravel Filter utilizes plastic plates that sit on the bottom of the aquarium. Usually, the arrangement this type of filter uses is simple; the gravel at the bottom of the fish tank acts as the filter medium. Unfortunately, the downside to this filter is that the debris continues to collect in the gravel bed. This can be corrected with regular vacuuming of the gravel, but it does add to maintenance.
Fluidized Bed Filter
Sand is used as the medium in Fluidized Bed Filters. Because of the sand supplying a large surface area, bacteria can multiply readily which helps keep the water oxygenated and clean. Although it is a good filter because it responds to problems in the tank quickly, it causes more problems with maintenance than other filters.
Lastly, the Sponge Filter is fairly simple. The water travels through a large sponge (acting as a biological agent) that is used after bacteria accumulate on the surface of the water. A simple filter to use and upkeep, it’s mainly used in hospital settings or fry tanks.