What kind of ballast is it? Electronic or magnetic? It should have a brand of some sort written right on it somewhere with all the numbers and schtuff. If it's not a ballast that's familiar in the reefing world (you may be surprised how many are) then the only way for you to tell is to use a PAR meter, but by far the best method is "Eff the PAR, how are the corals doing?!"
