Well, after a couple of days of a crystal clear 150g tank I walk in tonight to a foggy tank. Not cloudy but appears to look like fog swirling around. I haven't started cycling yet. I have a 50g sump and no skimmer yet. 200lbs of rock 100lbs being live, 4" sand bed. I'm also running a circulating pump that runs through two house canister filters, sediment and carbon. Any thoughts?