Your post is a little confusing to me, anyway. Your planning on using 36" lights over a 90G? 90G is typically 48" x 18" x 24" so Im going to go with those..
2 of these http://www.hellolights.com/superactinicr2.html
2 of these http://www.hellolights.com/aquasun2.html
1 of these http://www.championlighting.com/prod...9&cat=0&page=1
1 of these http://www.hellolights.com/484xcoraqpch.html
output on a 90, sure...If you keep most everything at the middle or top. For the effort and $$, your should consider VHO
setup if your not going MH
. Penetration is a factor and 18" with NO
, its going to be pretty dark at the bottom of the tank. This is of course, unless you want to stick with mushrooms and maybe some yellow polyps, etc (And it'll grownt he heck outta some algea ; )..The 36" NO
is 30W. So indeed you would be over driving the tube and thus causing it to vary from its intended wavelength much sooner not to mention dimmer still as you won't get near the coverage you need. Rather then replacing your bulbs every month or 2, consider spending the $$ on the proper equipment. Much beyond LR
, in a 90G @ 18", NO
even at 40W will not make you or your corals real happy..