My cichlid tanks are heavily stocked and therefore require heavy duty filtering to ensure that the aquariums' inhabitants stay healthy and are not subjected to polluted water. From day one, I decided that I wanted large, efficient, reliable filters for my aquaria. This, to me, meant buying Eheim external filters. Aquarium filters have three possible functions: chemical filtration, mechanical filtration, and biological filtration. Chemical filtration is not often used, but can be utilised to adjust water conditions (adding peat to soften water, for example). Mechanical filtration is removal of solid particles from the water. This is the ...  Read the complete review