Originally Posted by DogFish
I've looked at few PAR38 bulbs most are 1000+ Lumens. What I can not seem to find is info on how high to mount them over a 15" deep tank (12" to the substrate.)
Please check post #12, you will find a chart of 6,700K PAR38 bulb with high reference. However, all values are in PAR not lumens because lumen is a unit for human eyes not grow light.