That looks like a pretty cheap off-brand light. The light would probably be plenty bright for your plants, but ballasts on fixtures like that one have way of flaking out after about one year.
If you're going to spend a hundred bucks could you spend a bit more and get a somewhat higher quality fixture, such as a Catalina Lights T5 strip. You might also find a pretty good 48" T5 fixture at a local hydroponcs shop.
That tank is shallow front-to-back. I bet it would be enough to light it up with just two T5s with good refelctors.