I have been running one 250 watt on a 35 gallon reef for about three weeks now... looks great to me. awesome perfect bluish light IMO. does not need actinic supplementation. Not sure about PAR. The intensiveness seems very strong to me, but on the other hand I've not ever seen a different MH bulb of the same wattage so have never compared. anyway, seems great to me. Most people however recommend iwasaki's with actinic fluorescence for supplementation of the spectrum. I will likely not follow that order; my next lighting system will likely also consists of the sunburst 12k. I just like it.