I use the all-glass tripple T8 fixture on my 90 gallon and it is
working great as a low light setup. I'm using the GE bulbs that came
with the fixture. The tank is gowing many low-medium light plants
without CO2 or liquid fertilizers, just a rich substrate composed of
Flourite, Flourish Tabs, mulm and a little peat. I also tried this
fixture on my 55 gallon with CO2 and it was quite good. If you're
looking for higher light, 4-6 tubes would probably grow just about
anything. The three I tried grew E.Stellata quite well in the 55
gallon for example.

Hope that helps
Giancarlo Podio