Let's see, I've tried out 400W 6500K Iwasaki's, 10,000K's, and 12,000K Sunbursts. I currently have the sunbursts running. I am now going in a completely different direction than before. I didn't like the Iwasaki because the color was significantly more yellow than the other two bulbs. The 10K was nice, but once I got used to the 12K's, even the 10K seemed a little yellow.
Between the three bulbs, I have not noticed a tremendous difference in coral growth or health, however I have noticed that my purple coralline algae bleached under the Iwasaki's and a more reddish coralline started to grow on the rocks.
Anyhow, I am now going towards 250W 10K double ended HQI's. I hear they are more bright than their 400W counterpart, and the energy savings is big for me. I am not too worried about the money I will be saving nearly as much as the lightening of the current electrical load of my tank. Everything is on a 20 amp circuit, and I am dangerously close to overloading it. Dropping down 300W(two bulbs) I think will go a long way towards that.
