Thanks for the input folks. I am actually running Geismann 13K bulbs on my 180. The main reason being it is a 3 x 150 watt fixture and I wanted to get the most Par out of them. they appear to be comparable to a 10K as far a colour temperature is concerned. I have 2 x 250 20K Aqualine Buschke bulbs over my 90 SPS tank and I am very happy with the look, I just feel I should be getting more growth. There are some very interesting articles on the Advanced Aquarist magazine site but for some reason I keep getting redirected away from the page I am viewing. One of the studies that really caught my eye was where they had tested the intensity of several bulbs over a period of time and thier data shows that bulbs lost about 30% in the first four months and only 6 percent over the next eight months. From the one year to 18 month mark it only decreased by about 3%. They determined that changing the bulbs after a year wasn't a lot different than waiting a year and a half. I was surprised by this. I tried to find the link to the article but like I said the site was being very difficult to navigate.
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