How the hell do you guys keep your sand beds so clean?! I use ro/did water, do my water changes all my water is crystal clear but my sand bed browns up all the time. I syphon it off but then it browns again.I've had my water tested, I'm color blind so I have a hard time doing it myself.it always tests fine.all my bulbs are brand new.I have plenty of flow.my skimming if fine.I don't get it and I'm getting frustrated