I've moved up my lights another inch. They were at about 10 inches above the waterline and are now at 11 inches. I'm going to try and raise them up to a total of 14 inches above the waterline over the course of several weeks. I arrived at 14 inches by calculating for the 80 degree optics in the Hydra, and wanting a 2 foot spread (tank width) at the top of the water. Hopefully this will reduce spotlighting which may have contributed to some bleaching of corals.

I used the following arc calculator to measure the apothem (height above water) given the optics angle and width.

http://www.handymath.com/cgi-bin/arc18.cgi?submit=Entry

2015-06-12T09:47Z[GMT]