Metal Halide without glass covering-UV rays

[islandcreation]

I was reading Anthony Calfo's new book and he talked about UV rays from halides. Can anyone tell me how much of a reduction does a piece of glass will have on a 250 halide? I used to have a glass piece on my frag tank which is only 6 inches in depth with the light 2 feet over it. I took the glass of actually it broke when I was making a new stand whne moving it. So now my zoas/palys aren't looking so good now. Some seems fine and the other not so good. Previously everything was doing well. Any thoughts?

[cbrguy]

Is the bulb a HQI? they are the only ones that need the glass. If it is you have to put a piece of glass on it again. It will kill everthing. It will give you a sunburn too! ;)

[fade2black]

Why not just replace the bulb? If I am reading this correctly, you broke the outer part of the bulb? Is this a SE or DE bulb?

[The Grim Reefer]

If you broke the glass UV Shield you do need to replace it. Just have a piece of tempered glass cut to size.

[islandcreation]

Its a single end halide bulb. I thought you didn't need a glass cover for SE bulbs? How much UV does a tempered glass or a glass in general reduces? Thanks

This is the glass piece that just shields the bulb. Not the bulbs glass itself.

[DarG]

I did the math for DE bulbs and it is just under 20%. But it would depend some on the thickness and type of glass.

You dont need it for SE bulbs.

[The Grim Reefer]

Yeah, if it single ended you don't need the glass, it cuts out about 20% of the light

[pjf]

The reef lighting website will produce a spectral plot of your lamp: http://www.reeflightinginfo.arvixe.com/

If it is a DE lamp, you will be able to select the spectral plot with or without shielding to compute the amount filtered. Shielding of DE lamps is necessary for safety & health otherwise UV-B & UV-C will literally fry your tank.

If it is a SE lamp, the built-in glass envelopes alone should provide UV shielding but I guess that depends on the lamp. Personally, I would take The Grim Reefer's suggestion and replace the broken tempered glass shield.

If you wish to check, purchase one of these Oregon Scientific Personal UV Sensors from Target ($20):
http://reefcentral.com/gallery/data/500/93304OS_EB612.jpg