Definition: Biological filtration is a filtration method that uses bacteria to break down waste by means of the nitrogen cycle. Some examples of biological filtration include: biowheels, ceramic rings in canister filters, bio-balls in trickle filters, porous inserts in power filters, under gravel filters, and sponge filters. These filters harbor bacterial colonies that break down wastes into substances, which are less toxic.
biological filtration
By Shirlie Sharpe, About.com
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