In my opinion, metal halides would be overkill on a 10g tank. Just get the compact flourescent lights and use the few houndred dollars you'd be saving not going with the mh lights and use it towards live rock, corals, ect. I've been running a 29g reef for a little over a year just running compact flourescents and I haven't had any problems are far as the corals being healthy and growing, just make sure to give them the suppliments they need.