I am actually running coralife super skimmer on my 30 gallon and do water changes every 2 weeks, once I do a water change it goes away then comes back before I do another water change. Also I don't know if anyone else has this problem, I have to constently clean brown algea of the walls of my tank every other day, and also my sand bed, I've tried even limiting the use of the lights to try and kill and it hasn't, any idea's.