Mercury Vapor Bulb Question

[AnthonyC]

(1) Do MVB's lose their effectiveness (ability to transmit UVB) the further they are from the enclosure? I have a 160watt MVB that is hanging from the ceiling about 3 feet above the enclosure. It keeps my baby sullys nice and warm (90-92 in the hot spot) but I'm concerned about them getting those nourishing UVB's.

(2) I know that sunshine filtered through a glass pane is useless but what about the above UVB shining through a screen. (Like the metal type that you would put on top of a glass tank)

Thank you for you help!

 

[coreyc]

You should replace your bulb's every 9-12 month they will still shine but the UVB/UVA will diminish having a meter would help you know when to replace them . The bigger the squares in the screen the more gets through . So the finer the screen the less gets through

 

[Madkins007]

Distance- UVB bulbs definitely dissipate over distance. The thing is that at the recommended height, it creates a pool of the proper intensity to generate the desired levels of UVB. The further away you move it, the more the key spot spreads out and the dosage drops- move it up a little and the dosage drops a lot.

Each type of bulb has its own specific characteristics, however, so without a map of the spread, or a UV meter, you are best off just following the recommendations of the bulb.

Unless the glass or plastic is designed to pass UV light, it will block it. The annoying thing is that various kinds of meshes block it as well to some degree. Figure that screen top is going to block about 10% in general. However... why do you need a screen top with tortoises?

 

[AnthonyC]

Madkins,
I need the screen b/c I have a very curious cat. I don't anticipate any trouble from her but better safe than sorry. The enclosure is about 4 feet of the ground but that height is nothing for her to "leap with a single bound". I should've included this info in my post. Thank you for the advice!
-Anthony-

 

[Tom]

The 160 watt bulb heats a large area. Its more for larger torts in larger enclosures. Even the 100 watt is kind of big, but they work just fine. I just use 35-50 watt regular incandescent floods for most of the year since my torts all get regular sun.

How much UV is filtered out by your screen depends on YOUR screen. There are lots of different types and ALL of them will filter out at least some UV.