How far up?

[SKRIZ]

The tank has 3/4" bracing and I will be using 250w mh in Lumenarc reflectors. How far above the bracing does the fixture need to hang? I have read 8", but is that the bulb or the bottom of the fixture? the Lumenarcs are huge, 24"L x 24"Wx 8"H.

I know heat can crack the glass pretty easily (by STUPID experience), so I need to make sure I get this right.

[charlie]

I would go at least the 8", probably 10" to be on the safe side. See what happens for the first week, and then adjust from there. Do you have any pics of the reflectors?
If you don't mind me asking, what they cost ?

[Ninong]

The tank has 3/4" bracing and I will be using 250w mh in Lumenarc reflectors. How far above the bracing does the fixture need to hang? I have read 8", but is that the bulb or the bottom of the fixture? the Lumenarcs are huge, 24"L x 24"Wx 8"H.

I know heat can crack the glass pretty easily (by STUPID experience), so I need to make sure I get this right.

Is this for your new tank? The one that is 119" x 34" x 35"? If so, how many of these are you going to have? In other words, are you counting on a single row of lamps to light the full width of the tank? If so, I assume you're going with at least four lamps, right?

Assuming all of the above is correct, I would position the lamps so that the bottom of the reflector is at least 10" above the surface.

If my assumptions on the number of lamps is incorrect and all you are interested in knowing is the safe distance above a glass cross brace, then I would say that the minimum safe distance for 250w lamps above a 3/4" thick glass cross brace would be 8" from the lamp itself to the surface of the glass. Make that 10" for 400w lamps. And if you had an acrylic tank, you would have to add 2" to both of those numbers to be safe.

I have heard of brand new 200+ gallon Oceanic tanks with glass cross braces fail because people put 400w metal halide lamps 4"-5" above the glass cross brace and I have heard of really large acrylic tanks fail miserably for the same reason. Acrylic is much more sensitive to heat than glass.

[Ninong]

If you don't mind me asking, what they cost ?

This may answer your question. They come in various sizes.

[SKRIZ]

Charlie, I paid about $100 each from www.aquariumspecialty.com
I'll post some pics soon.

Ninong, all is correct. New tank. 4 lamps in one row. VHO for supplements. As far as spread goes, the reflectors do an awesome job of coverage (I tested it be placeing the fixture directly on the brace for about 5 minutes. the coverage was really good.). So, the safe distance is 8" from the bulb itself to the glass. But, for better coverage, you suggest 10" from the bottom of the fixture to the glass? (that would be really really high!). If, the reason is light spread, then I can play with the height a little, as long as I stay a minimum of 8" up, right?

thanks

[charlie]

This may answer your question. They come in various sizes.

Thanx, I did enuf searching yesterday, I found that too. I have heard some really good thngs about them!!!

[Ninong]

Charlie, I paid about $100 each from www.aquariumspecialty.com
I'll post some pics soon.

Ninong, all is correct. New tank. 4 lamps in one row. VHO for supplements. As far as spread goes, the reflectors do an awesome job of coverage (I tested it be placeing the fixture directly on the brace for about 5 minutes. the coverage was really good.). So, the safe distance is 8" from the bulb itself to the glass. But, for better coverage, you suggest 10" from the bottom of the fixture to the glass? (that would be really really high!). If, the reason is light spread, then I can play with the height a little, as long as I stay a minimum of 8" up, right?

thanks

I was mainly thinking of light spread. You should play around to see how it goes. I don't think you should go lower than 8" from the lamp itself to the glass brace. And if you ever go to 400-watters, you would want to increase that by a couple of inches.

Just see how it looks and how hot the glass brace gets after you set them up. The people who ran into problems usually were using 400w Iwasaki 6500K lamps placed less than 6" above a glass brace but with a fan blowing across the space between the lamp and the glass. Then if your fan goes out when you're not around, you're in trouble.

[SKRIZ]

great! I think I will start at 10" from the bulb and go from there..

Now, can anybody help me with the canopy?

[charlie]

Now, can anybody help me with the canopy?

As in???????????????????????????????

[SKRIZ]

How should I construct it? What material? I will be constructing a pivot mechanism so that the whole canopy can "swing" out of the way, so it needs be very sturdy.

[charlie]

How should I construct it? What material? I will be constructing a pivot mechanism so that the whole canopy can "swing" out of the way, so it needs be very sturdy.

I wish I could help you more, I am definitly not a carpenter.