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FAQs about Metal Halide & Halogen Light Fixtures Heat and UV Shielding

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Metal Halide UV    2/5/12
Hi WWM Crew,
<Hello Ken>
I have a 37 gallon reef tank with 150W 20k Dual ended Metal Halide over it.
However my canopy is open on the back. My fixture has a UV glass cover but there is a small portion of light on top that is exposed and unshielded and is being emitted upwards (upwards to the back since the font of the fixture is closed) the ceiling and the back wall. My question is, will UV light bounce from the ceiling and the wall that could be potentially harmful to people in the house? I keep the backside and the top side open to reduce the heat from the MH.
<Should be no problem as long as you do not look directly at the source from a close distance.  HQI lamps produce some UV-A which is much safer than UV-B or UV-C.  Tanning booths generally use lamps emitting UV-B which causes tanning or burning if exposed for an extended period.  UV-C radiation is produced by lamps most often used for germicidal purposes and are the most dangerous form of UV radiation.> 
<You're welcome.  James (Salty Dog)>

UV Shield?   4/19/11
Hello crew,
<Hey there Sam.>
I was unaware of this before, but apparently with the 150 watt HQI lights in my 24g JBJ nanocube I need to retrofit it with a UV shield?
<You should not have to if it is the included fixture. A "UV" shield is merely a piece of glass below the bulb.>
I'm not sure if this is true at all, but assuming I were to place a small fan blowing air from the back of the tank under the lights out of the front end, would I be able to avoid any plastic melting from the heat it puts off?
<It could help, but plastic will fail if it is directly under the light and the light is too close (within a few inches) anyhow.>
If the UV rays are really that bad that would be futile, but seeing as the person who suggested it was on yahoo answers, I don't know what to think.
Assuming I do end up needing a UV shield, are you aware of anywhere that sells them for a good price?
<Just a thin sheet of glass that can be had at most hardware stores.>
The website mentions nothing of a UV shield in regards to the lighting so any information you could provide would be most appreciated.
Best wishes,
Sam Sutonovski
<I am sure you have read the double vs. single envelope bulb in the single vs. double ended bulbs. In the end it is a good idea to have some sort of glass between your bulb and the water to keep a hot bulb from getting splashed, which BTW will 9 times out of 10 just end in salt on the bulb rather than a broken bulb. If your JBJ is in stock working form there is nothing to worry about here. Scott V.>

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