Green Algae Problem with new tank

[Sam Samy]

Hello All:
I've just upgrade my 48 Gallon tank to a 90 Gallon with new 400W(6500K) metal halide and 2 X 110 VHO Actinics. My problem is that I'm starting to see green hair or green branch type algae growth on the tank glass and on some rocks. I've never had this problem with my 48 before. The new tank has being running for about a week, with my 25W UV. The Nitrite/Ammonia/Phosphate are all 0 and Nitrate is 5ppm. PH is 8.3, salinity 1.025, temp average from 76 to 82...

I've been scraping the aglae off the glass and the rocks, but do not understand why this is happening. The only thing I can think of is the new lighting system for the 90 gallon...

Your thoughts and comments would be greatly appreciated...Thanks...