HOLY CRAP!!! A 15 gal with 150 W MH? Thats hella light bro! AWESOME! (as long as your not cooking everything - LOL)
I keep my blastos in indirect light, fully shaded for the most part. They are definently a low-light coral IME, everytime I try to move them into even remotely direct light, shrivel, shrivel, shrivel down they go. Not a fan of light in general, let alone bright light.