Selecting between aquarium filters can be confusing for a first-time buyer, considering that there are so many choices available from different brands. Filtration for aquariums can be classified into three categories – mechanical, chemical, and biological. Mechanical filtration helps in getting rid of particulate waste and suspended particles in the water, while chemical filtration basically helps in removing toxic materials. Biological filtration ensures that the water is oxygenated enough and has adequate bacteria for fishes to thrive.

If you are confused about buying a fish tank filter, below is an overview of the options.

  • Sponge filter. Also called the air filter, these filters work by forcing the water through a material that feels like sponge, using an air pump. The sponge allows the bacteria to thrive and the system ensures biological and mechanical filtration.

  • Power Filters. If you want a filter that can ensure all three types of filtration, this option should suffice. The filter hangs on the back or side of the fish tank and sucks up the water, which then passes through a filter for mechanical filtration. The water also passes through carbon, which ensures chemical filtration, while biological filtration is done inside the cartridge. Expectedly, such filters are great for smaller tanks and are expensive than sponge filters.
  • Canister filters. For fish tanks of 40 gallons or more, canister filters are great and ensure mechanical, chemical and biological filtration at the same time. These are bigger than power filters. With a pressurized system, these filters ensure better chemical and mechanical filtration. Many agree that biological filtration is not the stronghold of such filters, but these are still popular with hobbyists.
  • Under-gravel Filters. As the name suggests, such filters are placed under the gravel and pull the water through the substrate to the tubes. Mechanical filtration is ensured as the water passes through the gravel, although biological filtration is not as great. Also, such filters cannot ensure chemical filtration. The substrate should be cleaned regularly, if you are using an under-gravel filter.
  • Internal Filters. If you have a fish tank that’s smaller than 20 gallons, you can go for internal filters, which are placed at the bottom of the tank. Some of these filters do need an extra air pump for better filtration at all levels – mechanical, chemical and biological.
  • Trickle Filters. Trickle filters are not as common but are used in some cases, especially for additional biological filtration. What goes against these filters is the complicated setup, which can be complex for new users.

  • Fluidized Bed Filters. The final one on our list is the fluidized bed filter, which is usually hunt on the back of the fish tank and the water passes through it. A separate pump must be used to push the water into the filter, and with the suspended particles, good bacteria grows on the surface.

If you want to get any of these fish tank filters, we recommend that you check all the details. There are websites dedicated with filter reviews that can be handy.