to answer your question, typically the light levels work like this:
less than 1.5 watt/gallon = low light
1.5 - 2.5 = medium to high light
over 2.5 = very high light (you NEED CO2 to prevent algae overgrowth)
but of course these ranges are affected by the type of bulbs used, their age, the aspect ratio of the tank (a tall tank is lit differently from a long tank) etc.
less than 1.5 watt/gallon = low light
1.5 - 2.5 = medium to high light
over 2.5 = very high light (you NEED CO2 to prevent algae overgrowth)
but of course these ranges are affected by the type of bulbs used, their age, the aspect ratio of the tank (a tall tank is lit differently from a long tank) etc.
