hello all, im doin some research for a custom sump and was wondering how often do an "average" person change/ wash their filter sock? i kno everyone's tank is goin to be different based on bio load and size. but just lookin for a round figure. ALSO if it would make any difference in encorporating a "pre-filter" to the drain before it passes through the filter sock? such as passing through a filterpad that would minimize the amount of waste entering the sock.