What is biological filtration in an aquarium?

Biological aquarium filtration is a complex process essential for clean, healthy water. The new sera video "sera siporax - biological aquarium filtration" explains how biological filtration takes place: Purification bacteria in the filter make sure that pollutants such as fish waste are being broken down biologically. They require a filter medium on and in which they can settle to fulfill their task. The filter medium must meet some criteria to make it optimally suitable for being settled by purification bacteria. Biological filtration is the process by which bacteria break down pollutants in the water. The bacteria require a suitable filter medium to settle on and in, and the filter medium must have certain properties to support the growth of the bacteria. The optimal filter medium should have a high surface area, with a pore size that corresponds to the size of the bacteria, allowing them to settle ideally. The filter medium should also have an open pore structure, allowing for water flow and connectivity between pores, to enable the bacteria to move and multiply. The combination of high porosity and high connectivity makes for high filter performance, and self-purification is also an important characteristic, where dead bacteria are broken down without residue by other bacteria.