Does anyone have any experience using a Red Sea Prizm Protein Skimmer?? I have one on my 55 gal FOWLR tank and it doesn't seem to accumulate a lot of sludge. I only change the cup every couple of months, is this normal? I thought it would produce more sludge than that. Is this a bad product? Should I invest in a better skimmer? Any advice would be greatly appreciated.