As I just suggested to someone else...
I have a 29gal. I use a 36" 2xT5HO (10k+Actinic(420/460)) + a 24" daylight 6500k fluorescent T8 for supplement. I wouldn't go any less than the 2xT5HO, that combo should work fine though. If you can stretch for 3x or 4x T5HO's you'll be far better off. Wattage wise, a good guesstimate is.. try to get to 100watts+ but not all lighting is equal at a given wattage.
My RBTA is healthy and well colored with my lights. With the lower light it may stretch a bit to increase area for photosynthesis.