Re: lighting comparison questions.....

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Posted by phnoxx on January 05, 2003 at 10:34:03:

In Reply to: lighting comparison questions..... posted by Glacius on January 04, 2003 at 00:15:45:

:first, since i started reading this forum a few days ago, seems like a lot of you use those reptisun 5.0 lights...i think those are the tube things that make uvb...but you have to use some other source with it to produce heat. am i mistaken?

You are correct. Any iguana enclosure outside the tropics needs a heat source, anyway, at least for nighttime heating.

:the things i use i *think* are called Power Sun. they are these 100 wat bulbs that screw into a standard fixture.

Yep; those and a couple of other brands of mercury-vapor lamps sold in some pet stores.

:first, is the setup i have adequate? (the lizard *can* get pretty close to the light (like 10-12 inches if she wants to climb that high)). does provide the stuff the lizard needs?

It depends on the temperature + UVB irradiance at the ig's chosen basking spot.

It might be a bit complicated, but here goes:
With the merc-vapor bulbs, heat *and* UVB are emitted at a constant amount from the one bulb. That is, if the basking spot gets too warm, the ig will move away from it, and be outside the UVB zone. Conversely, if the bulb is too far away, the UVB will drop off to levels that are too low to sustain skin synthesis of vit. D3.

With fluorescent UVB-emitting tubes the heat output is minimal, so the tubes can be kept very close to the lizard's skin (within 6 inches, in my setup). This keeps the UVB irradiance per square centimeter of ig-skin nice and high. Then, in addition to the tube, a light (or two lights, or a light and a ceramic heat emitter) is used to regulate the warm-side temperatures (where the UVB tube is). A very accurate and inexpensive way to regulate the light's (and heaters') heat output is to use one of the vivarium thermostats such as ZooMed's models. With the warm-side lights run by the thermostat, and the UVB fluorescent tube in place, the temps stay optimal, and the ig can bask at will. UVb irradiance stays high. I keep a UVB tube in the cool zone, since my ig is large and his enclosure is large, so he gets even more UVB while he is in his cool mode during the day. (I've kept green igs for about ten years, and right now have just one big green ig, along with Cteno. species.)

The thing with iguana basking/UVB setups is, the igs don't regulate their own UVB exposure, because they respond only to temperature. With merc vapors, the UVB output is emitted along with all the heat; the heat can't vary at a given distance from the bulb. If the temps inside the cage rise to a certain level, the ig will move out of the UVB zone. With fluorescents, this does not happen, because the thermostat regulates the seperate heat-producing elements in the cage.

:anyway, is one setup better than the other?

I think the fluorescent setup is better, because it assures better UVB skin-exposure.

:and, i've also been reading (this seems to reference the reptisun 5.0 bulbs) that they have to be replaced every six months.

That is the conservative approach. Many, if not most of the fluor tubes last much longer, but you need a UVB meter to check up on them. I happen to have one, and many tubes are proving to last over one year so far. If I didn't have a UVB meter, knowing what I know now that I do have one, I'd locate a local person who *does* have one, and ask if I could test my tubes with that meter. You can buy these meters on-line for about $150, and keep track of your own UVB irradiance (ideally, at least 35 micro-watts per cm^2 for vit.D3 synthesis). If you have the money, it's the way to go, because int the end, you'll make the money back by keeping tubes that you'd otherwise toss out.

No, I don't own stock in the meter company :-)

:normally, the bulbs i get are pretty damn expensive...like 30-37 bucks. what i do, is wait until the store has them on sale (20-30 bucks) and get several of them. i burn one, and save the rest until they are needed. well, if these things have an "expiration" date...should i not be doing that?

I'm not sure about whether vaps' UVB decays over time. They usually blow-out early.

In the interest of full disclosure of information, here is a site that points out some possible problems with in-home merc vapor lighting:

http://www.anapsid.org/mercuryvapor.html

Roger

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