How far to hang 175 watt halides?

[MarkO]

last night I finally powered up my halides and not really to my suprise, one of the glass tank covers shattered. The glass is 1/4" non-tempered and the halide bulbs were about an inch above the glass.
Right now, the bulbs have 2 1/2 inches of separation. Is this too close or too far?
Thanks in advance.
Mark O

 

[NateHanson]

Do you need the glass covers for some reason? I'd remove them, personally.

 

[RobboT]

If they're DEs then you need the glass for UV protection. If they're moguls then you dont. I believe that Sanjay recommended 6" to 9" for proper light distribution and to minimize the heat impact to the tank from the bulbs.

 

[MarkO]

I prefer a glass barrier for many reasons:
1. reduces potential splashing onto bulbs
2. basic electrical concern for when I am messing around back there
3. heat and more importantly the evaporation factor. Even with the glass, I think I'll be losing between 1-2 gallons per day... especially in winter.

 

[NateHanson]

Do you mean to keep heat in? Or reduce heat transfer from the bulbs? I thought glass covers created a greenhouse effect that heated the tank more than an open top.

 

[MarkO]

Yes, keep the heat in. I don't use heaters (never have), so I try to heat the tank with the bulbs. In the summer, I run a fan (thermally controlled) across the top of the water for evaporational cooling. This has kept my tank temp between 75 and 82.

 

[NateHanson]

That's interesting. Sounds like you've got things in a good balance. That's 2 175w over a 150, right? Is that what you had over your 90 as well?

 

[MarkO]

I plan to have two 175's over the 150. They'll be placed about a foot from each end of the tank, centered. Then I also plan to run a pair of 96W PC fluorescents (only have one in there now) in the middle. At least that's the plan. When I get around to adding rock/corals to the middle, I may supplement another 175 MH to the center or replace the twin 96's.
On my 90, I had the 2 175's and a 96W 10k and a 96W actinic. Seemed to be more than enough lighting.
Since the 150 is about 5" deeper, I just moved my intense lighting corals closer to the top.