Well the way ATI fixtures are designed to cool ,is the air is pushed down from the fans on the top of the light and the air is forced out one end of the fixture. Blocking the end of the fixture is like covering the top of your toaster and being mad your toast got burnt.

6 inches of space between the fixtures and no canopy should provide sufficient air space for cooling. There is very little hot air coming out of the end of the fixture.
I think that the plastic reflectors were a design error and the ballasts are not heavy duty enough.
The overheating issue does not explain failures in both fixtures.

I've got a 8 bulb ati led hybrid and love it. Super sleek looking fixture and for your size tank 2 3' fixtures or 1 5' fixture be good.

Yeah I agree that 6" should be enough space , were both fixtures pointing the same direction, or were they blowing into each other? I guess with 6" space in between you must have had a little overhang on both ends of the tank ?

The fixtures themselves are 46" and with a bit of an overhang the space was about 5 1/2".
Both fixtures were pointing the same direction, the exhaust outlet of one was blowing into the side of the other, but with the intake fans on the top and sagging acrylic lens they come with, there was lots of room for fresh air to enter and hot air to excape.
Since I've replaced the initial ballasts, I haven't had any problems which makes me think that the original ballasts were the problem. (in addition to the plastic LED reflectors)

Glad to hear they are working well now , I have the 36" 8 bulb hybrid and love it.

hey,

a lot of great input so far!

I was thinking if I go with kessils i'd take advantage of their form factor and run them as pendants. 2 rows of 3 on a 6'ish long tank. to get better coverage than running a single row of 3 down the center. I think it would look fairly sharp over a rimless display. just wondering about shadows and sps coloration.

of course i'm considering the ATI hybrid. there seems to be a large following on that fixture. reviews seem to be good for the most part.

I am also considering the PACSUN hybrid, it looks just as nice as the ATI.
http://www.pacific-sun.eu/new/cache/...5b3b843aff.jpg

As you're well aware, there are so many other factors affecting SPS. "IF" you got all that dialed in perfectly, running LED will showcase your work well. While I still give 400w radiums the win on color, I only say that from hundreds of hours of staring in my tank under both systems. Nobody ever looked at my tank under LED and thought color sucked. Just me :) And that was from maybe a 5% difference in color. I did have a couple pieces completely change color, but the other 100 pieces did well with only a slight drop in that pop we strive for with SPS.
I think a hybrid system will give you enough of all the desired features that you'll be happy with the purchase.

I hear ya on the MH.

I still remember rocking the single ended 400s with huge reflectors. only took 2 to light my 180 and you could put sps everywhere! add 2 VHOs and Boom youre done!

if it weren't for the size of fixture/canopy/hood needed for it, i'd consider them for sure. if only I was doing an in-wall with a fishroom.

having said that, the DE MH fixtures I've used just didn't cut it on spread. i'm sure if you raise lights high enough the spread would be better, but I don't think I've ever had a fixture more than 8" above the tank.

You'd need more than 2 DE for sure. Jamie ran 2 x DE on his 120 with pretty good results!