Help! Glass Lens Replacement Proving Difficult

[emissary43]

I just set up my frag tank with a used fixture I have been kicking around for a while but never used. It is a 6ft fixture for 3 double ended MH bulbs with a fan on the end to vent heat. Pretty standard design. But the person I picked it up from had broken the glass lens and I just replaced it with two pieces of some "double thick" (about 3/16") glass from Orchard Supply. Apparently that is insufficient because it cracked after about 30min. I am very lucky it didn't break enough to fall in the open top system.

Does anyone have any advice for what glass to use??? The fixture lacks a brand name but the replacement glass should be
68 1/2" x 9 1/4" I am trying to find a similar fixture online to by the replacement lens but have yet to succeed.

[emissary43]

How dangerous for the coral is it to run double ended 150watt MH without the glass? I have read about the UV burning corals and assume it is true but are we talking fast or could I run them for a couple hours a day just to maintain them for next week? Basically is darkness more dangerous than UV for LPS/ mostly Acans and Brains?

[Discustopia]

It's not normal glass, when I broke mine the local shop was kind enough to pull a piece out of a display light.
DE bulbs need the glass and should only be removed by a professional for research studies.

[eznet2u]

Take one of the other pieces down to them to measure.
Have them cut it and send it in to temper.
Replace.

You will not like what UV can do to your coral in a couple of hours.
On the other hand you can go for days without light.

[melev]

You need to get an accurate measurement to a local glass shop and ask for the piece(s) to be tempered glass. 1/4" should be fine.

Do not run them without the glass shield, as the UV radiation will bleach your corals in mere hours.

[emissary43]

I thought so. Yeah I figure these all made it through over 60 hours of shipping at some point so a few days till I can fix this won't kill them. But I am sure they won't be happy.

Tempering sounds expensive, what do you imagine the turnover time on getting that done is?

I have been thinking of building a T5 fixture and ditching the MHs this might be the weekend to do it.

[melev]

Tempered is merely a process of baking it. If you tell them you need a piece of glass 8" x 36" with polished edges that is tempered, it won't be long to wait nor costly.

I was looking for three 20" x 20" pieces of 1/4" Starfire glass, polished and tempered for $180, and they'd have them in a week. What you'll need is smaller, and you don't need starfire unless you just demand greater clarity like I do. :D

[emissary43]

That is really helpful, thank you. I will hopefully find a glass place open on the weekend to get things going asap... or I will just run down to the workshop of the company I work for and throw some PCs together that will tide things over until I can get the glass.

[areze]

buy the replacement glass...

you can get it from whoever makes the pendant/fixture. 14$ for a reefoptix glass.

PS. UV from the bulbs is extremely harmful, will kill anything alive in very short order, and will also harm you, burn your retinas and your skin.

this is the stuff we use to kill everything in the water column with UV lights, it gives us a sunburn in weak doses outside...and so on. dont mess with it.

[emissary43]

buy the replacement glass...

As I stated in the initial post if was able to figure out the brand of this fixture or a comparable size I would have bought the replacement part. And I new that the UV was bad but I was more curious if any one had actually tried it to see how quickly it causes coral damage. I am not sure which damaging UV wavelength it produces and what water penetration it has. Probably UVC but I am only guessing.

Anyway I figured I would ditch the older noname fixture and build a nice new T5 setup instead.

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http://i283.photobucket.com/albums/kk284/emissary43/DSC00896.jpg

[melev]

It burned my corals in a few hours, on two different occasions. Once the glass broke off cleanly, leaving about 50% of the bulb exposed. I found the glass in my reef and it looked like a giant test tube. I couldn't believe the light was still lit, and grabbed my camera first before turning it off. ;)

The second time, the glass cracked as well, but the end stayed put, creating a 1/8" gap for the UV to radiate out, and it burned a straight band across a number of corals in a straight line.