if using T5HO on a non-co2 setup, i would aim for approx 1wpg. This would equate to one 48" 54w T5HO bulb over a 55g tank. im using two 54w bulbs on my 55g. it has pressurized co2 and i can barely manage to keep the algae under control. it took a lot of fine tuning in the beginningbl00;2825949;2825949 said:Not to derail the thread, but I'm also curious how a 48" t5ho would do on a 55-75 gallon tank that's not using pressurized co2 (I'm using flourish excel now, but moving to diy co2 soon)?