I have a proclear 125 wet dry filter that has an overflow box on my 110 tall FOWLR. I have been reading several threads about lowering my nitrates and I have come across a few threads that have said that the filter sponges could be contributing to the nitrate level. Could this be the case in my tank? There is a filter sponge in the overflow box that all the water runs through, in the sump there is a filter pad that the water overflows onto and then finally there is one last filter block that the water has to go through before being returned to the tank. I have about 125lbs of live rock stacked in my tank as well. These filters usually get cleaned out every couple of weeks when i do a water change and they seem to catch some pretty nasty stuff, especially the one in the overflow box and the filter pad in the sump.