I've used a pressure filter similar to the "PowerClenz" but without the self cleaning feature. Personally I would be a little sceptical about the self cleaning because mine is not and it does take a significant amount of rinsing to thoroughly clean the crud out of the filter media. I can't see a short term backflow of water doing much of a job so that's probably why they recommend weekly cleaning. Possibly other users of the "self cleaning" variety could comment further. I use a pressure filter rated at "3500 gallons" and 1200 gph on my small 500 gallon pond & 20' stream with a 1000 gph pump. Given the height of the head, length of hose and bio falls filter at the far end I would guess that actual flow is around 700 - 800 gph. I'm no expert but I would think in general terms, the lower the flow rate, the better the filtration. The larger the filter capacity, the less frequent cleaning is necessary and that would result in less back pressure on the pump... and greater sustained flow. My pond was fairly cruddy prior to installing the filter and I found that cleaning every 3 weeks was more than adequate because the "clean" indicator had not popped up yet and flow through the filter was still excellent. The down side of an oversized filter is a bigger hole and more space required for installation.
