“Dirty” Filters are Definitely the Best
There is this strange saying among veteran pond owners and aquarists that goes like, “dirty filters are definitely the best”. This does not imply that we should never clean our pond’s filters, but that we should never clean them thoroughly, especially if they are the “biological” type. This is so because we run the risk of wiping out entire “friendly” bacterial colonies if we clean our filters thoroughly. You would probably do better to implement multiple (but less thorough) cleanings, and only on the parts where you don’t see the shiny, gelatinous layers commonly referred to as “biofilm”. This are actually the colonies of “friendly” bacteria themselves. To be always “on the safe side”, apply this “less thorough” method of cleaning even other filters.