i have an aquaclear-500 on my 40g and have cut one of the sponges they sell for it as a per filter on the intake. I've been doing this for several years now and it has cut down significantly on the need to clean the filter box out. you'll need to clean the sponge frequently (bi monthly is what i do). My cherry shrimp cruise it for tasty tibits constantly. The biggest issue i have with it is appearance, i'll try to attach a photo but if that doesn't work you can look at my other posts (i only have a few) for some photos I posted under the plants section to get a visual . . . not real pretty but all cities have grates over the drains. I'd tried a tighter celled sponge (it was a black material) that you buy already formed but I found that it plugged too quickly, which made the impellor rattle as it struggled to draw. the AC-500 sponge I have now is one I've had for yrs even with an occassional bleaching. I squeeze the filter out and use the nutrient rich water on my house plants . . . bonus!