I agree with Ocelaris. If you want to use MH, a 250 watt bulb with a good reflector at the right height will cover that tank nicely. Tullio at Reefbrite recommends that exact set up at about 16 inches above the tank for ideal coverage. I wouldn't worry about odd encrusting patterns as TexasReefer82 has experienced (his description sounds like very fast and aggressive growth due to some kick a$@ mh lighting)... that's an anomaly... I don't think you'll find anyone else with those issues, especially with a quality reflector at the proper height.