Mixing filter media
One thing that i see very little written about on this site though is about the importance of combining different filter materials in one filter chamber (forgive me if i´ve missed a post on this). The number of surface loving bacterial species in a filter qaudruples as a rule each time a new filter media type is added due to a reduction of species dominance. This is due to the fact that certain bacteria like certain surface types more than others. If you have different surfaces then no one species can become and remain dominant. A wider range of nitrifying bacteria species also means the filter becomes more biologically robust. It isn´t that important exactly what filter material you use (given that surface area isn´t too bad for a given filter material) but extremely important that you mix your filter medias - not layered like we aquarists love to see but mixed up with each other in the same chamber the way mother nature likes it