Originally Posted by reefkprZ
watts is energy consumed to operate and in the end has very little to do with the overall light output. 35 watts of PC is far more intense than than 35 watts of regular output flourecents. 35wats of T-5 is far more intese than the same wattage of PC, its the par or intensity of the output that really makes a difference, watts per gallon was invented as a rule of thumb when there wasnt much in the way of knowledge cocerning light out put in the hobby. now we know more but most people cannot wrap their minds around the concept that input has very little to do with output, I have to be honest, I dont completly understand all of it by any stretch of the imagination. I slice dice puree and blend, but I know watts pergallon is about as usefull as a bucket of air. I would consider it one of the least accurate rules of thumb persisting in this hobby just refusing to die an honorable death.
but how are people going to know whether itll be good enough for the tank? lately theres been threads about t5 and mh, but not many people are going to honestly know for sure what the tank will need.. so my question is.. with t5 and mh, how is one supposed to know whats the best t5 or mh fixture for their tank when all you see is so and so watts per bulb when you look online at things?