Interesting thing happened today. Both bulbs kicked on prior to supplemental lights, so I could really see what was happening. Both bulbs horribly green while warming up. Then both bulbs looked like a nice crisp white a bit later. An hour later left side bulb, the original good one, looks perfect, the right side, original questionable bulb looks green/dim. I notice the fan is going on the left side of tank but not yet on on the right side. Later,30 minutes, the right fan is now running and both bulbs look great, nice crisp, white. This is continuing to be perplexing. I thought with the fans blowing on the bulbs you could possibly experience a greener, dimmer bulb. I have what appears to be the opposite effect, read about this here on the board. I need to watch it for a few more days to get a true correlation but I do like the look of both bulbs now that the fans are running. The only problem was the other day when I initially noticed the difference between bulbs the fans were running. Who knows, I am still not sure whether to send this bulb back or not.