At AquaCave, we offer some of the best selection & best prices on aquarium filters and filter accessories for you marine, reef, and freshwater aquarium. The Three Types of Water Filtration (1) Mechanical filtration of water is done by passing the water through a screen, or a thin piece of sponge, or through a floss material, all of which remove pieces of debris from the water. (2) Chemical filtration of water is done by passing the water through small pieces of carbon or zeolite, which is a natural mineral. The carbon or zeolite remove molecules such as ammonia from the water. (3) Biological filtration of water is done by certain types of bacteria that live on gravel, on the surface of glass, on ceramic ornaments, on plastic plants, on bio-balls, on floss, or best of all on BIO-Wheels.