hmmmm might be nitrates, but i do do 50% waterchanges a week, but the wet-dry overflow is a piece of ****, my dads firends friend did it, and at first i was like WTF IS THIS!! i had to drill to make the openings bigger. And it does more harm than good, plus its a pain in the ass to clean out, i cleaned it out yesterday and it was full of gunk n **** its liek that every week, might be the source of the nitrates, not sure though gunna have ot test the water.
ill try taking pics but the batteries i use arent stong enough to power my digital camera whic his bull****.