Yea...my nano-cube has a 150W metal halide in the hood only a few inches above the water as well.
I stay on top of water changes, run a skimmer, and try not to overfeed in order to keep nutrients low. Nuisance algae is definitely present, but isn't taking over the tank by any means. Livestock all seems happy...but I do need to light acclimate most of my low light corals by placing them either in the corners of the tank or under an overhang / in a cave.