Metal Halides, how far away do they have to be??

[buggle]

I just got my lights from Hellolights.com My questions are:
how far from the VHOs do the MHs have to be? If I stick them both under the same reflector, they'll be about 1.5" away from each other. Would this be OK or would it get the VHOs too hot? Also, how high from the water does it have to be? Hellolights recommends 10" but since this will be a retrofit under my existing hood, it'll only be about 3" from the water? Is this OK. Stupid me bought the VHO retrofit kit AND the MH retofit kit. Now I have a $30 parabolic reflector that I don't need. Anyone want to buy a brand new (still has the blue film on it) reflector?

Thanks.

Buggle

[griss]

Buggle,

I have run VHOs within 1.5" of MHs with no problems, so that should not be an issue.

However, with you only mounting these about 3" from the water I see a potential problem. If the MH bulbs get splashed with water they will most likely crack or shatter. Since it is best (for gas diffusion) to have an open top aquarium, you are better off getting a hood that will allow you to mount your lights 8-12" above the water surface.

Griss

[buggle]

Thanks for the reply griss. Glad to hear that 1.5" is OK. Not happy to hear what you thought about being 3" from the water. What is I got some glass and put it in between. Would this be OK? I'm afraid this would be my only option aside from getting a whole new hood.

Thanks.

Le

[griss]

Originally posted by buggle
Thanks for the reply griss. Glad to hear that 1.5" is OK. Not happy to hear what you thought about being 3" from the water. What is I got some glass and put it in between. Would this be OK? I'm afraid this would be my only option aside from getting a whole new hood.

Thanks.

Le
You could put a glass top, however this will cut down on the amount of gas diffusion between the tank and atmosphere, which could lead to depressed pH. Also, the glass will block some of the light penetrating your tank. Combine that with salt build up getting on the glass and you reduce your lighting further. Not to mention having to clean the glass top all the time.

FWIW, many people do use a glass top on their tanks with no apparent problems. So this sounds like an option you can at least give a try.

Griss

[buggle]

I guess I'll give that a try and deal with cleaning the glass. I can't burn a bigger hole in my wallet with getting a new canopy. I have a 20 gallon refugium below my tank. would that help with the pH? Thanks.

Buggle

[goofball310]

There are a couple of things that I would like to add about the problems you may face:

1. Having the top on will lead to heat problems
2. Having the halides 3" from the water will lead to heat problems
3. Before I make a fool outta myself for mentioning 1 and 2, how big is your tank and what wattage are the halides?


Just a little info:

At one of the LFS that I go to, they suspend their canopy about 2 feet above their tank. This can help you with having to put the top and having the lights 3" over the water.

I also noticed that you don't want to put out that more money, so you might want to consider this instead of putting $500-1000 on a chiller.

[buggle]

It's a 55 gal with a 20 gallon fuge. I plan on running fans under the canopy as well as one blowing on the surface of the water of the fuge. I have two 48" VHOs and one 250 W MH. What do you think? Thanks.

Buggle

[lllosingit]

I just feel I have to warn you about using a glass top between the MH bulb and the water. If the bulb is to close to the glass the glass will get hot and will also break if it gets hit with any water.
If you only have 3 inches now I imagine that would put the the bulb/glass and water way to close to each other.
What kind of hood do you have?
you could always get some wood cut to the correct size and put it between the hood and the top lip of the tank to raise it up.

[goofball310]

I hate to be the bearer of bad news, but you might have some heating issues.

If you look at my signature I have almost the same set-up you do. When my first halide turns on, my temp would spike up 5 degrees before I got the chiller (I'm running my tank @ 79 degrees). My halides are only 3-6" above the top of my tank and I have a fan in my canopy and on top of my sump.

What temp range do you plan on running your tank?

If you plan on running it higher in the temp range that might also help.