Filtering Out the Myth of Aquarium Filters

There are three main types of filtration: biological, mechanical and chemical. Mechanical filters aid in the physical removal of solid particles. Chemical filters purify the water by chemical reactions that take place at the cellular, microbial, and atomic levels. In most cases, it is best to incorporate all three types for optimum results. This article focuses on biological filtration. Biological filters encourage the growth of nitrifying bacteria that breakdown ammonia to less toxic chemicals. This breakdown process by the bacteria is known as the Nitrogen Cycle.

In the Nitrogen Cycle, waste products generated by fish and invertebrates, along with any dead organisms or uneaten foods, are broken down by bacteria into ammonia. Ammonia is extremely toxic to all of the aquarium inhabitants and is broken down into nitrites by the aerobic bacteria Nitrosomonas. Although nitrites are not as toxic as ammonia, even at low concentrations in the aquarium, they can still be harmful to fish and invertebrates. Other aerobic bacteria called Nitrobacter, act in a similar way as Nitrosomonas and further breaks down nitrites into relatively harmless nitrates. Nitrates, at low to moderate levels, will not harm most fish or invertebrates, but can be the source of algae problems if not controlled by chemical filtration