I've been using a 150watt DEXM bulb on my 60g corner reef aquarium for exactly one year. And for the past 4 months my tank's health has rapidly declined. Nuissance algae was taking over the entire system. I did multiple massive water changes, with no success. I checked the water coming out of my RO/DI and it was reading 6ppm. Tank chemisty was ideal also. so I've been racking my brain trying to figure this one out. At the expense of all of my corals I might add. Well I replace my bulb last week, and I noticed that the element casing had turned an orange/red hugh, and seemed to have changed the spectrum from white/blue to red.....In less than a year. (That explained the incredible algae growth) After I replaced the bulb the problem was corrected in about a week. So word of warning, check your DE XM bulbs for this red/orange hugh that forms on the element inside the bulb.