My main concern in my tank at the moment is the diatoms..the light brown on my aragonite. I comb the sand a little to make it disappear but it is right back the next day. I use all RO water, my nitrate,nitrite,ammonia is all at 0...I run my daylight halides(2x150) 8 hrs a day. I have some green algae on the back (it's not long hair like it's just on the glass., but I keep up with the other 3 sides. I have a 75 gal by the way. the LR doesn't have any hair algae but there are different colors on it along with coraline algae. I am guessing I need more flow. I use a mag 7 return in my sump to pump up to tank and I have 2 RIO 800 in the DT. I need suggestions on what kind of powerheads to get if that is the problem. Right now if I move my PH down at all they blow my aragonite around. Please..any suggestions?.,. I want alot of flow but I don't want sand everywhere! Alot of people told me the flow is my diatom problem on the bottom..true? oh..am I using the wrong attachment for flow direction? I use the attachment that is wide with slit across it for like a wide stream...