It's going to depend on bulb choice and reflector design. With the strongest 150w bulbs in good reflectors, it should be OK. But, in general, it would probably be best to keep the more sensitive and demanding corals near the top of the tank.
with 2 x150W, one a electronic ballasted with a really nice pendant reflector, and the other is and Giesemann 150w pendant. with a splash barrier how high must a 150W be off the top of the water for heat and bleaching to not occur?
You can put it as close as you want, as long as it's not getting in the way and you have reasonable expectations (i.e. I wouldn't put it closer than 3 or 4" because it'll make it hard to reach in the tank!) 150w DE is not really *that* bright that it'll cause problems, unless you put low light stuff right under it up high on the rock.
you can keep sps at the top with even so so reflectors. the key phrase is "at the top". at the top on a 120g is no different than at the top of a 30g. there is the camp that believes 150w Mh arent appropriate for a full blown sps tank which I sort of agree with (too many placement stipulations, dependence on water clarity and slow growth) BUT that being said I have mostly sps all 6-11" from the top using 150w x2 sunpod and 20k bulbs and no issues. colors are as they should be, growth obviously could be better but they do grow. For a MIXED tank with SOME sps at the top 150w work just fine. I have monti cap frags on the bottom of the same (17" tank) and for kicks put 2 frags from the same cap in my 14g biocube with stock pc and they have retained their color and thrive/grown in the several months they've been in there. all sps arent created equal, there are enough moderate light requiring sps and even acro's where no one would even expect they are doing so well because you chose carefully and not expect the weak lighting. for example tri-color validas, ORA's roscoes blue, green mili's, most monti's ect ect ect will do just fine under 150w where a acro hyacinthus or humilis would be served better under the best 250w or 400w combo there is to be had.
<a href=showthread.php?s=&postid=15483368#post15483368 target=_blank>Originally posted</a> by BCreefmaker will i get quite a bit more growth from 150W 10k instead of 13k or 14.5k? or will it hardly be noticeable?