[fishytime]

I think four sols would be more than enough on a 20" deep tank.....unless you are planning on putting sps on the bottom of the tank against the front and back glass, than the lower light areas will be beneficial to the "less light thirsty" corals....Im in the same boat as you....my new tanks footprint is 30" x 84".... I flip flopped back and forth between the sols and the radions.....in the end the bling factor of the radions won out and Im gonna try four and pray that that is enough....I also rationalized that my tank is only 24"d so I didnt need the penetration of the sols and would be better off with the better spread of the radions....I will be doing my aqauscaping mostly down the center of the tank to allow for more swimming space and better flow......I agree that if you go with the sols, get them to order the ones with the 70 degree optics....I would start with three and go from there....