lighting in a 37 gal tank

[bowz75]

I currently have a 37 gal. Eclipse tank with a few sad looking plants. I still have the standard lights, 2 natural daylight F18T8. 36 watts total for a 37 gal. tank = almost 1 watt per gal. When considering plants what are the numbers that correspond to low, moderate, and bright light. Thanks.

[Wasserpest]

It depends a bit on tank size, but with good reflectors, and good bulbs (T5, PC or MH) I'd say

<1.5 W/gal low light
1.5 - 2W/gal medium light
>2W/gal high light

With less optimal reflectors and not so good bulbs (T8 or T12) maybe

<2 low
2-3 medium
>3 high

Wattage is just one thing, what matters is how much light makes it into the tank.

Of course, what is medium to me could be a totally different thing to you, so that's all extremely subjective.