I am wondering what this stuff is. Ever since I took my filter media out and started just running the filter for water movement, my nitrates have come way down to about 10-20 (from 40-60). But now I keep getting this brown stuff on the back of the glass and sometimes on the front. It almost looks like the diatoms I first got way back when my tank cycled. Is this normal? All of my parameters are great! My skimmer is working well and all my fish are happy! Oh yeah, after I do my water change I do put a new carbon pad in my filter for a few days just to help clear up any gunk. If this stuff is normal, should I just keep using my magnet cleaner to get rid of it? Thanks.\n\nI wish I could take a picture, but it does not show up on a pic.