Folks talk about watts per gallon and you need more for plants (there's a whole lighting subsection on this forum).
There are many possibilities.
For a quick fix I'd get a
glass canopy and put a
Coralife F/W T-5 Aqualight Double Strip Light-48" on it. That would give you closer to 1 watt per gallon, which is not much, but a start. It also depends on the kind of plants you have.