my pond is a 300g plastic preform. my filter is a 5g bucket with a 550gph pump inside. before i do a WC or clean the filter, i hook a hose oto the return of the pump and i actually get into the pond and blow water in between the rocks and along the bottom so that the sludge gets sucked into the filter. i let it run a while, the clean out the filter. the remainder of the sludge get vaccumed out with a pond python. I also use lots of aquatic plants to help witht the waste.