MH lighting advice

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ronj

Blue Tang
Joined
Nov 28, 2005
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4,490
Location
Destin,Fl
i am about to add some 250w MH's to my display...how high do they have to be above the water?????my canopy will only allow about 5-7" ..is that enough???? i may put some clams in there after a while..i am also changing this tank from softies, to sps corals..i already have some monti's and i just got an acropora today...any advice would be great!!
 
ok, i just measured..i have 8" from the water line to the top of my canopy..i will have to subtract an inch or so for the reflector, so i have 7", or about that
 
This is from Premium Aquatics website...

Installation guidelines
We recommend hanging your halide hood or pendant. Usually about 8-12" from the tanks surface. This lets the halide light spread out and being hung, you have less heat problems if any. You can also install your halides into a covered canopy. We would recommend 12" tall with strong 4" cooling fans (icecaps work great). You can install in hoods as low as 6", but protecting from water splash is very important and controlling heat could be a problem.

As Bob stated (and like I mentioned on that other thread), you want to keep the bulb from being splashed with water. Here's a photo of my bulb after touching it with a wet finger. It took some of my finger print with it as you can see and caused the bulb to crack which I found out is a "no no" to use even if it still lights up because if the UV shield is broken, it can burn your corals. I ran one set of halides 9 inches off of the water and another set 12 inches and both worked fine. :)




 
will my lights work with my canopy?? i can only mount them about 7" over the water
 
will my lights work with my canopy?? i can only mount them about 7" over the water

Yes...You'll be fine. You will just have to keep an eye on heat as well as keeping the bulbs dry...


Here's what Jeff (The Apprentice) posted on a thread of mine that was similar to this one...


Previously posted by The Apprentice
Krish witrh my 75 gallon Tank My PFO fixture is 5" above the water line and I have 2 each 250 watt Metal Halides

Here's the thread if you would like to browse through it as well:)
http://www.reeffrontiers.com/forums/showthread.php?t=14250&highlight=inches+pose+problem
 
Tangs = Lots of water spashing

The only diffrentce I see Ron is I have the PFO ACROLIGHT Premium Hood that has a Tempered glass shield between the bulbs & the Water
But I am a little closer on my 75 about the same 6-7" mark as your looking at but again I have a PFO Acrolight on it as well.. Here is a shot of them..


Yes...You'll be fine. You will just have to keep an eye on heat as well as keeping the bulbs dry...


Here's what Jeff (The Apprentice) posted on a thread of mine that was similar to this one...




Here's the thread if you would like to browse through it as well:)
http://www.reeffrontiers.com/forums/showthread.php?t=14250&highlight=inches+pose+problem
 
so do you think i need a sheet of glass mounted between the water and bulbs????
 
???????

Ron I just don't see that many people with the sheet protection.
I just didn't want to have one of my Tangs bust a lense while I was gone and have a coral burned tank when I found it. Plus I liked having my lights in a contained Fixture;)


I believe the majority of fellow reefers don't HTH...Jeff



so do you think i need a sheet of glass mounted between the water and bulbs????
 
HTH...Hope that helps! He's saying the majority of reefers don't use protective covers, but he does for the simple fact he doesn't want a tang to bust a lens or have a tank of burned corals.:)
 
oh..cool...i am worried about splashing though...i will try to figure out something..if anyone has any ideas, please send them my way!!!!!!!!!!
 
could i just mount any thin piece of clear acrylic or glass over the water???? could the heat from the bulbs melt the acrylic or break the glass????
 
Depends on the thickness of the acrylic, it could possibly bend so I wouldn't use anything too thin if you go that route, but glass is what they use on a lot of the pendants to protect the bulbs so glass will be fine. Not sure if it has to be tempered though. Be careful with heat as well if you use something to cover your tank:)
 
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Ron have you considered the height off the water from the actual lamp or the 7" is the height of the reflector bottom? The only time you would have a problem is when fish would jump & splash water that high but then even 12" could get wet in that case.
 
Not sure if it has to be tempered though=yes

Yes Ron if you go with a sheild I recomend tempered glass mine are 1/4" thick on my fixtures.;)
Sorry I confused you in post 10..Jeff



Depends on the thickness of the acrylic, it could possibly bend so I wouldn't use anything too thin if you go that route, but glass is what they use on a lot of the pendants to protect the bulbs so glass will be fine. Not sure if it has to be tempered though. Be careful with heat as well if you use something to cover your tank:)
 
I took the glass shields out of my luminarc on the recommendation of the manufacturer. He said they were not needed. I suspect that damage from a little water splashing on most single ended bulbs is quite rare. Don't put a layer in front of the bulbs if at all possible. It will lower the par values
 
I run 2x250W MH and I am about 7" above the water. I too use the glass shield. I figured it does lower lumens a bit, but I have plenty of lighting either way. It does prevent a problem however. I have actaully seen a tank where water hit the bulb, bulb exploded, glass everywhere in the tank. The guy told me he was still finding/pulling out glass 3 years later.
 

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