How often should I clean the filter media?
I have had an aquarium for 5 years, and I have only cleaned the filter so far but never replaced the filter materials. My question is, if and when I should replace the filter media of an external filter?
Prefilter materials (in particular, filter wool!) should be regularly and thoroughly rinsed or replaced at the latest when they start to become clogged. Biologically active main filter materials need only be changed when they are clogged so strongly that even cleaning them (i.e. with biofilter materials: rinsing with aquarium water) does not lead to considerable water flow improvement. Generally, a well funktioning and correctly dimensioned biofilter is very convenient - the less maintenance it reauires, the better!
Dr. Bodo Schnell