Cyanobacteria problems...help

[krschulz]

Six months ago I started my 90 gallon tank and have (in the past 6 weeks) run into overgrowth of cyanobacteria. I have 4 Accela 1000 powerheads (256 gallons per hour) running constantly, a protein skimmer and T5 lights about 8 inches above the tank. The fish and corals are thriving but I always have cyanobacteria clumping my substrate together. I have removed most of the substrate, except the stuff I can't reach under my live rock; I have used erythromycin to knock it back (which it did for a couple of weeks); I have added the newer koralia 3 (856 gallons per hour) which has blown my substrate around and helps.
So, is this a flow problem that I should get rid of the Accela heads (they don't stick well)? Should I add another koralia turbo pump? What is the formula used to determine if my flow is adequate? Can you have too much flow?
Should my lights be lowered/heightened?
Am I overfeeding and getting this growth? Hard, green algae has covered the bottom glass of the tank and my snails are busy working at it. Do I cover the algae with substrate so it can't get light and hopefully dies off?
How do you clean under the live rock when you can't reach with the siphon/vaccuum? More flow?
All my chemicals are within range all the time except a bit low on potassium even with daily supplementing. Any help would be appreciated.