glass between MH and water?

[~SIRENA~]

I have a 400wt MH fixture that is attached to a diy canopy. It is about 18" above the water, but I do not have any type of glass or covering for it. Is it necessary? Will I run into problems later on?
Thanks,
Adriana

[ROB2005]

I think that with that height above the water, you should be fine. But let me ask, do the bulbs you have double ended or single ended?

[~SIRENA~]

Thanks! and single, why?

[ROB2005]

I was just checkin, with DE bulbs, you have to have a UV glass shield to prevent the UV light from damaging to corals and the sort. SE you dont have to have it as the outer envelope captures the UV light.

Just dont make too much of a major splash though *unlikely* as any good amount of water that splashes on the bulb will shatter them instantly.

[rickh]

At 18" above the water I would expect a great deal of light into the room. I would use a UV shield.

[hyperfocal]

I've got a 2" long burn scar on my forearm, reminder of another good reason to put glass between your bulb and the rest of the world. Of course, I haven't installed glass yet but that's because I want to have a few to brag about if I'm ever on the Orca with Quint, Hooper and Brody...

"See this one? Metal halide. TWO HUNDRED AND FIFTY WATT metal halide..."

[Mr James]

Lower the light. I wouldn't put glass or anything else between the light and the tank, with the exception of egg-crate to diffuse the light somewhat. If I read you dims right on your tank, 28" is awfully tall. You were smart to go with a 400w, but I would lower it to about 12" off the water surface.

[S_Stoney_S]

If it shatters, dont breath in :), inhaling heavy metals doesnt do you any favours.

[Mr James]

Why would it shatter?? The light is what we are talking about correct??

[ahullsb]

It is burning so hot, that if water splashes on it, it could very likely burst.

[bk_market]

at 18" the water probably wont get to it but if u decide to lower it then put some kinda of glass

[WaterKeeper]

What was mentioned here is that a screw in mogul based lamp has a glass shield around the arc tube. It keeps the inside tube from breaking if splashed and also contains the glass if the inner tube breaks. Another thing it does is that it acts as a UV shield. MH lamps emit dangerous amounts of UV radiation and that can harm your eyes and often harms the tanks inhabitants. The shield prevents that.

Double ended HQI tubes are just the arc tube without a shield. Arc tube temperature reach over 1200_º C so water splashing on the tube will usually shatter it. Also the quartz glass of the arc tube transmits UV very well. Enough so that you never want to look directly at an unshielded HQI. There a simple glass barrier is all the protection needed as plain glass does not pass UV.

[Mr James]

I have always run SE MH bulbs roughly 12" off the water surface. I've never burned my arm (knock on wood) and I have splashed the bulb numerous times without any bulbs breaking. JMO

[rickh]

I've got a 2" long burn scar on my forearm

I have a 2" long scar on my forehead from the surgery to remove the skin cancer caused by Mr Sun. I would always use a UV shield on your MH or make sure everyone in you fish room wears sunscreen :)

[ReefGirlSara]

hyperfocal, I have probably a very similar scar on my forearm...from my 175 watt MH. It's a screw in and it's about 12 inches off the water. I'm pretty sure I have splashed it more than a couple of times, and it's never broke, but it does make me kinda nervous (the thought of it breaking). Just don't burn yourself, that was one painful burn, and it kept forming more and more layers of tiny blisters- it took forever to heal, and the scar is steal pretty ugly 1 year later.

[RGRDGR]

seems the safe concensus is to install some glass..

[hyperfocal]

Glass: Mandatory on DE bulbs, a good idea on SE.

[WaterKeeper]

Right you are hyper. The shield tube on the single ended offers pretty good protection from heat shattering and UV but the DE lamp is an exposed arc tube running at 1200 degrees Celcius. As it is high quartz (what the HQ in HQI stands for) glass UV passes right through it.

[~SIRENA~]

Thank you all for your info. You are awesome. I will keep try to put some glass between the water and MH. I'll figure something out. :)

[m2434]

<a href=showthread.php?s=&postid=11049803#post11049803 target=_blank>Originally posted</a> by Mr James
Why would it shatter?? The light is what we are talking about correct??

I was working on a tank once and the 250MH got a little splash of water. I heard, cling, chink etc... and quickly ran to unplug it, luckily I got to the plug before it exploded, but there was a big 4" crack and a bunch of little ones, a few seconds later, who knows...