Know Your Filters!

The key to a successful aquarium is a proper filtration system. The best line of defense against an unhealthy aquarium to understand the different types of filters and how they work. There are 3 different cater goes of filters:


  • Mechanical filtration is where water is forced through filter media which catches particles suspended in the water in your aquarium.
  • Chemical filtration occurs when toxic chemicals pass through a resin or media. Some chemical filtration products target specific excessive nutrients or chemicals from the aquarium.
  • Biological filtration is the breakdown of different bacteria. This is called the nitrogen cycle where waste products, food, and fungi are broken down and create ammonia. Ammonia is toxic to the aquariums inhabitants. If there is sufficient space for the beneficial bacteria to grow, your nitrogen cycle will work properly. A biological filter is designated by the amount of space made for the bacteria to grow on.

Using these different filtration methods, we can take a look at the various types of filters! Each type of filter is different and can be used for different types of tanks, or just your personal preference.

HOB Power Filter

One of the most common types of aquarium filters is the classic HOB (hang on back) power filter. These types of filters combine the use of mechanical, chemical and biological filtration.

  • Aquarium water is sucked up through the siphon tube.
  • The mechanical filtration begins by the water passing through your filter pad or floss.
  • Chemical filtration occurs by the water flowing through the carbon, that will remove toxins from the water.
  • Lastly, the biological filtration begins inside the filter cartridge. If your filter has a bio-wheel, there is added biological filtration from the water passing over the biological filter. The water flows from the wheel or cartridge back into the aquarium.

HOB filters can be used for fresh water and marine aquariums, and are appropriately sized for tanks ranging from 10 gallon all the way to >100 Gallon! Pisces recommends: AquaClear Power Filter. 

Sponge Filter

Sponge filters are generally used for low flow aquariums, such as nursery or hospital tanks, breeding or aquariums with small fish or invertebrate.

A sponge filter is powered by an air pump where water is forced to pull through the sponge-like material. The sponge is capable of producing biological and mechanical filtration because beneficial bacteria live on the sponge.

Sponge filters are typically inexpensive, ranging anywhere from $5 – $40. Pisces recommends: Aquatop Classic Flow Sponge.

Canister Filter

Canister filters are a favorite by hobbiests and are built for large aquariums (40 gallon and up). They are great for cichlid, saltwater or planted aquariums. Unlike the sponge and FOB, canister filters are  large and are usually stored underneath or behind.

Canister filters work by mechanically and chemically pressurizing the water, by forcing the water through fine material that can trap smaller particles. After the water has passed through a series of filter media, the cleaned water is then pumped back into the tank. They have a long flexible siphon tube that connect the filter to the tank, with a return “water bar” that spreads the outflow of water through a long bar. Pisces recommends: Fluval Canister Filter.

Sump Filter

A sump filter is normally divided up into sections that we call chambers. The chambers are created by using dividers that perform a very important task and therefore must be installed properly. These excel in the biological part of filtration due to part of the filter media is exposed to aquarium water and a significant amount to air. Being exposed to both air and water creates a large colony of beneficial bacteria to grow and process waste products.

The first chamber contains a mixture of biological and mechanical filtration. Several hundred bio balls have been put in the chamber first, these are then topped off with several layers of mechanical sponge filtration.

The water then flows down through the mechanical and biological filtration and enters the second chamber via a gap under the divider.

Finally, the water flows up through biological bio balls and over the second divider into the third chamber which contains a pump and heater. If the second divider is not lower than the first divider then the water will not flow into the third chamber, it will flood the whole filter. The final chamber that contains your pump must be designed to hold plenty of water, the bigger the tank, the more water it needs to hold.