UV protection under metal halides?

[AJT]

I have (3) 400 watt MH. They are single end screw in Radium 20,000K. Do I need to put a piece of glass or plexiglass under to protect corals from UV. If so, is there a special rating or type I need to look for?
Thanks
Andy

 

[Len]

Nope. Mogul bulbs with outer envelopes (like your Radiums) emit an insignificant amount of UV-A (and no UV-B or C). The only halides you need to UV shield are the unprotected double ended "HQI" bulbs

 

[AJT]

Thanks, that is what I had heard but I thought I would check with the experts.

Andy

 

[D.W.L.]

May I add this for a reference. Its of a different opinion.

http://www.aquarium-design.com/reef/uvlighting.html

 

[Len]

Thanks for the post, Doug. Funny thing is I was quoting from a previous article Dana wrote. Apparently, he changed his mind due to his more recent findings.

 

[D.W.L.]

Welcome Len.
Just figure its interesting reading when this topic comes up. I dont think many runs tops though. I use a glass lens on one of my 400,s but dont think it helps much. I have partial tops on my tanks, but also glass only.

Tried the Lexan tops. Eventually got to hazy and warps under the halides. I cant see any difference in the corals one way or the other. So far that is.

 

[Anonymous]

I would almost think the concern for UV-A would be on our eyes not as much as the corals since they are used to sitting under tropical sun for 12 hrs a day. Of course it would be nice to see how much of the UV-A is below 295nm where sunlight cuts off. I am surprised the glass envelope doesnt do more to take out the short-wavelength UV light. I know my MH canopy is suspended and a fair amount of light is spilled out into the room. I wonder if I should bring in my 400W Iwasaki I just got (not mounted yet) and take a spectral power distribution of it. I'm curious to see what it is.

 

[Len]

This is the article I was basing my original comments on:
http://www.seaplace.org/riddle.html

Again, I presume D.W.L.'s article is more recent, so I would go with that data.

I'm also surprised that the outer envelope doesn't absorb much UV-A or UV-B. But the bottom line is single ended metal halides don't emit much UV (per Riddle's own analysis and Sanjay's/Morgan's). UV-A is roughly half of full sunlight, and UV-B (the more dangerous of the two) a small fraction. Whether or not the outer envelope does or does not effectively remove UV, it doesn't matter much. The net UV emitted is nothing to worry about.

 

[Anonymous]

Ooops I had my A and B and C mixed up. Boy now I look silly .

 

[D.W.L.]

Leonard, Thats a good article also. It seems to be earlier, but seems to have some reference to the other article. Perhaps that was his line of thinking, thus the tests he did. Also the end of your article, seems to agree with the one I provided.

The reference at the end of the article I provided, refers to some 1998 material. So it must be later. Anyways I will ask him.

 

[AJT]

Thanks for all your replies. I found some plexi. at a place near me. The company recommended Cyro OP3. I went to their web site & asked them about it. Subject
I need a piece of plexiglass to put under 3 metal halide lamps on my 200 gall...

Discussion Thread
Response (MOHAMMAD ABSI-HALAB) 06/13/2002 02:54 PM
Andy

Thank you for using the CYRO Industries TechKnowlogy Center. Our regular business hours are Monday through Friday, 8:30am - 4:30pm (EST). If you would like to speak to a Technical Service Engineer directly for further assistance, please call (203) 795-6081. For a list a ACRYLITE® Acrylic Sheet Distributors, click on the link below:

http://www.cyro.com/cgi-bin/mqinterconnect?link=find

All recommendations made herein are believed to be reliable, however, such recommendations are made without charge and without warranty, and on the express understanding that CYRO Industries assumes no obligations in connection with any such recommendations.

The maximum recommended continuous temperature for ACRYLITE OP-3 acrylic sheet is 160°F. ACRYLITE® OP-3 acrylic sheet filters out about 98% of incident UV light. Click on the link below to view a light transmission curve for the material.
Title: ACRYLITE OP-2 and OP-3 sheet UV transmission curves
URL: http://cyro.custhelp.com/cgi-bin/cyro.c ... 0982951435


We cannot comment on how this material will perform with the light that you have. We have never done any testing on such lights. My understanding is that these types of lights come with filters which should be kept on there. I am not sure how hot it gets there, but if you stay within the recommended temperature, then there should be no problem with the melting.

Please contact us should you have additional questions.
Customer (Andy Tanguay) 06/13/2002 12:46 PM
I need a piece of plexiglass to put under 3 metal halide lamps on my 200 gallon saltwater reef tank. I have been on the web talking to other aquarist and UF-3 was recommended. I called my local supplier & they mentioned your product OP3. The reason for this plastic is to reduce UVA & UVB light from entering the tank & harming corals. My lights are 400 watt 20,000K Radium. There are fans to cool lights, but they still get pretty hot. My question is: Is this a good product for this purpose? At what temp. will it yellow,warp, or discolor. ( will my lights melt it). How much UVA & UVB will pass thru OP3? If this is not the right product , do you make a better product or recommend one for this purpose.

Thank you for your time

Andy Tanguay

Question Reference #020613-000001
Product: Sheet Products
Sub-Product: ACRYLITE® FF acrylic sheet
Category: Sheet / Films Physical Properties
Sub-Category: Optical Properties & Transmission Curves
Contact Information: [email protected]
Date Created: 06/13/2002 12:46 PM
Last Updated: 06/13/2002 02:54 PM
Status: Waiting



If your issue remains unresolved, please update this question here.

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Mohammad Absi-Halabi
Technical Service Engineer, Sheet Products
CYRO Industries
Tel: (203)799-4065
Fax: (203)795-5800


DO YOU THINK THIS PRODUCT WILL WORK??????

ANDY
--------------------------------------------------------------------------------

 

[Len]

If you want one of the highest transparent UV absorbant material I've come across, try http://www.framingsupply.com/museum.htm.

Xwild in #reefs pointed out the site to me. If you guys haven't already, you're invited to check out our chatroom.

 

[AJT]

Len,
I can not get that link to work? Do you know another place I can get what you are talking about?

Thanks
Andy

 

[Len]

Oops. Included the period by accident:
http://www.framingsupply.com/museum.htm

That should do it.

BTW, acrylic/plexiglass under halides is a bad idea. They'll warp very quickly unless very thick.

 

[suckair]

Smoke it down.. The UV makes them color up

 

[AJT]

Len,
One more question. I called a local art/framing store to see if I could get Image perfect in Houston. They did not carry it, but mentioned another glass called Tru Vue that they had in stock. Have you ever heard of this brand? The ad says something about a UV coating. I am pretty sure a coating on anything near a reef is bad news.

Thanks

Andy


http://www.artaffairs.com/Showcase/truvue.asp

 

[Len]

To tell you the truth, I have no idea whether coated glass is usable under this much heat. Best thing for you to do is ask TruVue about whether it's suitable for high heat applications. I know that TruVue makes a "museum" glass too that is highly UV absorbant with high transmission. You can go with these if TruVue says coating is ok. Image Perfect (the site I referenced you to) uses a etching process for their glass that is presumably better suited for our needs.

 

[AnotherGoldenTeapot]

It's important to remember that light transmission depends on the thickness of the material too.

Even though polycarb is nothing like as good as acrylic, you can get it quite easily and cheaply in big bits only 0.8mm thick (used for corrigated roofing).

Being so thin it will have light transmission properties comparable to other material that are usually supplied as 3mm or thicker.

Mounted at a distance of 20cm this thin polycarb stands up to the heat generated by 250W HQI bulbs - it does got hot, but only to the point of just being able to hold your hand on it.

 

[D.W.L.]

Thats a good site Leonard. I must read more later.

I just happen to be a believer in covers on my tanks. Not in love with the evaporation tons of water into the air of my home and I get enough air exchange through the two tanks feeding into a 70 gal sump, skimming, scrubbing,etc.

My tanks are in my basement fishroom. Always cool here, so trying to heat them is my main problem. Anyways, always looking for a new type of cover.