Red slime algae Phormidium HELP

[addictswife]

I am not real new to this hobby but new to this problem. Primarily SPS tank with tangs and a few other fish. We have developed the red slim algae. This is Phormidium found in low nutrient water with high light. Water is testing good for everything. We use Elos and Hanna test kits. Recently switched to LED's. How do you get rid of this stuff? We have siphoned it out but it is fast growing and just keeps coming back with a vengence. 210gal with 2 MP 40s so flow doesn't seem to be the problem either.

 

[Reefing Madness]

Are you running those MPs at full bore? If not, i'm betting on flow being the issue. If you are, did you acclimate your tank to the LED lighting? If you did, I'd pull the 3 day lights out to rid your tank of it in the mean time.