“Mechanical Filtration” refers to passing dirty water through some form of sieve to remove impurities. Fluval filters use foam, carbon and Pre-Filter media to do this job. These materials force water into many channels where it goes up, sideways and through complicated pathways before passing out of the filter. This complex path increases actual filtering area many times the measurable volume. Carbon or charcoal also remove liquid impurities from water by trapping them in the carbon matrix.

“Biological Filtration” is extremely important. It reduces organic poisons created in the aquatic chain of life. Urination, defecation and respiration by fish produce ammonia as a byproduct. Excessive feeding, dead or decaying plant and animal matter also produce ammonia as it is degraded by bacteria. Ammonia in aquarium water is deadly to fish even in minute quantities. Fortunately, there are “helpful” bacteria that use ammonia as an energy source. Nitrosomonas bacteria reduce ammonia to nitrite.

Nitrite is also extremely toxic to fish. In new tanks, levels of both nitrite and ammonia can build to toxic levels rather rapidly if there are too many fish and not enough beneficial bacteria. A second strain of bacteria (Nitrobacter) reduces nitrite to less harmful nitrate. This can only be removed by regular water changes.

These important bacteria require a place to attach and multiply to become effective for biological filtration. Fluval filters provide a suitable substrate to promote a healthy population of bacteria with standard Fluval media. Foam inserts and Pre-Filter provide a generous surface area for biological filtration to develop. Other media in the filter case also provide some attachment nodes. The BioMax filter media has been specifically developed to accept and promote bacterial population on the extremely porous surface area of each ring. The pore size has been engineered to offer ideal size for thriving beneficial bacteria colonies. Used in the middle chamber, BioMax is a powerful addition to ammonia and nitrite reduction within the filter.

“Chemical Filtration” refers to active change of water conditions by chemical means. Ammonia and a number of other toxins can be reduced chemically. Peat is used to soften and acidify water naturally for specialized breeding purposes. There are a numerous ion exchangers and water conditioning media available for many specific jobs. Crushed coral or coral sand is often used to buffer, harden or increase alkalinity. Canister filters allow a number of chemically oriented jobs to be combined with other filtering activities.