I think MH equates into more light than the wattage indicates, but much depends on how high the light is suspended. I'd venture you'd be served by going with CO2.
I went from MH to overdriven fluorescents (on a 75g) when I went to planted from reefs (I couldn't get reliable sitters with the reef). I still have pearling on the low light plants.
I went from MH to overdriven fluorescents (on a 75g) when I went to planted from reefs (I couldn't get reliable sitters with the reef). I still have pearling on the low light plants.