Originally Posted by Nix
In a nutshell if someone says he/she has 2w/g it can mean anything from low light to high light, depending on the bulb/reflector system?
It's really rough, this rule.
You got it.
Another glitch is the tank size... the rule is not totally linear. For smaller tanks, 2W/gal could be low light, while for large tanks it could be high light. There is also a "threshold" for really small tanks. Don't try to light your 1gal nano with a 2 Watt bulb!