Hi,
I had a 12 gallon planted Eclipse last year, but it came with a weak fluorescent light that was fine for java fern/moss and aponogeton. I assume that the T5 means it is incandescent? If so, that will definitely have to go.
My Mini-Bow tank came with an incandescent, but I was able to find a CF (compact fluorescent) in the Wal-Mart pet section of all places. I would try to find a CF that fits before I started thinking about retrofitting--- that gets expensive! A 9 watt CF would be plenty of lighting I think. I had 10 (?) watts on my 2.5 gallon Mini-bow and I got massive growth hehehehe.
As far as CO2, I would recommend it, but not CO2 injection. In small tanks even a little CO2 can wreak havok on your water chemistry if it's not monitored closely. Try SeaChem's liquid carbon supplement (Excel I think? It's been too long geez)... Fluorite should be fine, but I'm an "onyx sand" type of guy myself, lol.