In defense of the WPG metric it is simply easy to calculate. Sum the value for watts on all bulbs (Assume ballast power factor of 1 and efficiency of all fluorescents is the same*) and then the tank size listed on the box (ignoring that it is calculated based on outside dimensions, full to the top, and no substrate) and divide!Anybody with the same (frustrating) experience?
You got it. :icon_mrgrIn 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.