my frag tank has 4 t5 and is a 20 long I believe, 30 x 12 x 12"deep
You definitely don't need to upgrade, unless it's for enhanced brighter color and more florescence, I find that 3 x 20 000k t5 h.o and a 10 000k, seem to enhance color's. When I turn off 2 x 20 000k, then leave 1 x 10 000k and 1 x 20 000k the color's don't stand out as much.