Ok so why the hell do I always have brown spots only in the corners of my glass from top to bottom?\n \nI also have to clean my glass with my big square Magflo every 3 days or so.\n \nI do not overfeed and I have plenty of light. I had this issue in my other tank. I have to use a brush as the spots will not budge with just the Magflo.\n \nAnyway I don't even clean the corners but once a week because it is much harder to do.\n \nI just want it gone forever. I just tested for Phosphates and got the big 0. I run ROX Carbon and have a HUGE skimmer and plenty of old live rock.\n \nI read it can be low oxygen but if that is even kind of true what can I do about it if that is the case. Put an airstone in the sump. There is plenty-o-movement from the skimmers return.