I kind of figured you it was unlikely to fry coral with T5's but I wasn't too sure, thought I'd throw it out to the experts and see what the ruling was.

Will it matter if the tank is only 16" deep, and I cram 8 bulbs over it though? Probably going to be mostly softies and LPS.

You could certainly get some bleaching of even Acropora sp. at 16" depth with 8 HO T5s - especially if not acclimated properly. And especially if a quality fixture with active cooling is used.


Steve,

That quote you were asking about isn't from the article. The PAR of 1100 is from the article but the portion about 2 x 250W MH producing this comes from Apogee measured values from a hobbyist's tank. While 1 250W MH produces the values you've reported the cumulative effect where they overlap with 2 x 250W MH could certainly produce that level of PAR at several spots in the tank - especially with a high quality reflector. For comparison see the picture below where 6 x 39W HO T5s in a crappy Tek light produced the PAR levels seen in the picture:

http://i85.photobucket.com/albums/k72/jartanyon/par.jpg

Fijiblue, the same hobbyist who was running the T5s in the picture above decided to try MH again with 2 x 250W MH over that same tank and found he was getting over 1100 PAR at the surface.

Ok, I agree with that kinda of output in the air at a couple inches. When I did my testing on my tank I did that then I started at 6 or 7" below the surface where it had dropped off from around 1100 to about 700, so it does attenuate quite a bit when you bring water and depth into play.

yes, VHO, PC, even NO will bleach a coral if it is not acclimated properly, I am assuming that the acclimation is proper and we are not dealing with that.

Steve