you can use them until you can get another one or a better light altogether, i got a buddy who is just starting out that has on of those over a 55 gallon with live rock and zoos, mushrooms, and polyps, they just won't thrive and grow and spread quickly. The more light they have the better so if you get some corals keep them higher up in tank on live rock until you get more lights.
Its those darn guys at pet stores that mislead people just to sell some of there stuff, i just watch guy at our pet store who has metal halides on his display tanks and other coral tanks sit there and tell a customer that the coralife power compact light that he stocks that is way over priced that it was one of the best lights on market for corals, i wanted to choke him out for telling a customer new to the hobby all those lies to buy a light for 400 bucks which is online for 198.00.