It depends, I ran (2) 48" Reefbrites and two other DIY LED strips together (4 total strips) over a 5', 110g reef...worked great. Depends on what you want, what you're going to "grow" and mounting options. I can say these Reefbrites are AWESOME! BUMP
What size tank? How wide front-to-back? If it's a skinny tank (like a 55g), it'd probably work, since this is a "real" ReefBright and not some Marineland or eBay cheapie. Coral placement can be adjusted to accomodate, and so can the height of the fixture. Bring it down lower if you need deeper penetration. 24" isn't that deep, and it's wide enough at 48".