Good write up, but I don't agree at all with the "rule" about how many LEDs to use. You can use various numbers of LEDs, depending on their power, on the configuration you use, the optics you use, how far they are from the top of the tank, etc. Here is one empirical way to determine the number: One Way to Design a Planted Tank LED Light
Thanks for pointing out the mistake hoppy.
Actually I read it on ledgroupbuy website's faq.
I have your excel calculator but could make it work
Maybe you can answer it then- If kept 5" above the water level, with 60 degree optics, how many LEDs to be used for a 60-P. [24"x12"x14"]