Thought it was in my other post, I use 8 bulbs, I know people who use 6 for same size tank so my numbers were based on my usage. Two Hydra 26 HD wouldn't cut it for me, recommended spread on those is 18x18 with a large drop off on 24x24. I know Red Sea has a deal with AI and pushed those and only 2 on the 350/XL425 deluxe models. Since my other LED's are all Radions, I would have probably gone with Radions. With the AI I would have gone with the 52's and same as with Radions, 2 minimum, 3 optimal. So being slightly cheaper it would have taken a little less time, but still years for me to break even. For some people the numbers work out for LED over T5, for me they do not. I don't worry about the extra couple bucks in the electric bill either. With 5 tanks running, not counting 2 QT also running at times, I wouldn't really notice.