Filter systems are very easily understood if you take on board these simple concepts.

Filters are designed to:

• Remove solid waste
• Create water flow and aeration
• Chemically clean the water

There are all manner of contraptions you can purchase and use in your aquarium for filtration. Provided they achieve these key functions optimally for your tank, then it matters little what their design.

Solids should be removed efficiently and by a means which is easily accessed and cleaned, without disturbing the tank itself. It has been found that the efficient removal of solid waste is the number one factor in determining the success or failure of an established aquarium. The aquarium volume should be turned over 1.5 - 4 times in an hour through the filters to give adequate chemical purification and aeration.

Chemical filtration is a complex topic and we will focus on the nitrogenous waste story in our brief discussion here. You can refer to more detailed texts for more in depth information.

Nitrogenous wastes are those produced by the fish, and decay of organic matter within the tank. The primary waste product is ammonia, which is toxic to fish in certain forms. The levels of ammonia will naturally build up in the tank after establishment, giving rise to the proliferation of bacteria, which use ammonia as a nutrient.

One particular type of bacteria (Nitrosomonas species) converts the toxic ammonia into the more toxic nitrite. The nitrite then acts as a nutrient source for another group of bacteria (one of which is the Nitrobacter species) that convert it into the much less toxic nitrate. This is utilised by plants and is removed when you perform a weekly water change.

The bacteria are on every surface of the fish tank and one of the functions of the filters is to provide an increase in surface area through the water flow for the bacteria to attach, proliferate and perform their chemical function simply by existing. The more the surface area the more the bacteria.