Acrylic and UV question

[RedEyeReef]

I have one of my 400w MH mounted over the center brace of my acrylic tank without any UV glass between the tank and MH bulb. Will the UV from the 400 bulb wear on my tank and multiply the possible chance of cracking the center brace? I have fans that control the heat from the bulb and surprisingly the center brace does not get very hot, no more than any other part of the top of my tank.

So by lighting through my center brace am I asking for future trouble?

 

[jlehigh]

Is your 400MH a double ended bulb or single?

The reason I ask is because single ended bulbs are already shielding the UV with the glass aparatus of the bulb. Double ended bulbs require an additional UV shield.

I would imagine you have a single ended bulb in which case I would say you don't have much to worry about. An unshielded 400W DE bulb would have probably already cooked your corals.

If the brace doesn't get too hot and you have a single ended bulb I think you are okay. How thick is the center brace anyway?? You can always reinforce it with a strip of acrylic fixed to the existing brace by nylon nuts/bolts.

 

[RedEyeReef]

My 400w are SE, I don't think 400w DE's are out yet. I know they are in the works. The glass envelope around a SE Bulb does shield some UV but not all after seeing different bulb tests, like Sayjay articles. It is that little bit of UV that gets through I am wondering about?

I believe the center brace is 1/2", maybe 3/8"?

 

[fishermann]

if you are worried about the center brace cover it with a piece of tinted acrylic you can buy as scrap at most glass stores or plastic supply shops or even just a pieces of neopreme or abs.

 

[RedEyeReef]

Any idea how much light I will loss from tinted acrylic?

 

[fishermann]

How wide is your brace, if it is not very wide like mine you won't loose much at all. The current brace defusses alot of lite, personally I wouldn't worry about it, there are alot of tanks out there that are as yours is without any problems.

 

[Thefishcouple]

RedEyeReef
I called the tech. dept at Polycast this morning and asked them about exposure to UV as this question has been coming up quite a bit lately. This is what they say; there acrylic is UVA safe for ten years which is also by the way the warrenty period, after that time it may discolor but it should not affect the intergrity of the acrylic. The other concern you have would be the continual heating and cooling of that part of the tank. If you keep it cool it should not pose a problem. It will however block all of the UV from your bulbs and I think you want some UV to reach your corals. That may defeat your purpose but that question would be directed better at someone like Mojo or Nikki. As far as the tank goes you should be fine.
John

 

[RedEyeReef]

fishermann,
My Center brace is about 17" wide, pretty big.

iapjohn,
Thanks for making the call. That answer is what I was looking for.