I know info gets lost in the search mode, and sometimes stickies aren't obvious. Since tegus are coming out of hibernation and basking regularly, it is a good time to change UVB if needed or redo an enclosure that maybe needs an improvement or two. i posted this quick message somewhere else and just thought it might make good food for thought here, too. Not my info, but from Dr. Frances Baines.
About tube lights:
"Tubes supply a diffuse "glow" with low intensity visible light, very little heat, and a fairly uniform UVB gradient, resembling natural UVB "in the shade" on a sunny day."
"Since they are not particularly bright light sources, fluorescent tubes can be situated directly above a reptile at fairly close range without, apparently, causing distressing glare. However, some do emit high UVB at close range and traces of UVC (1-3 uW/cm²) can be detected at the surface of all tubes tested, hence a safe minimum distance of maybe 3 - 4 inches would seem advisable.
The diffuse glow from a fluorescent tube is not focused into a beam, and hence does not project a great distance from the lamp. To achieve UVB coverage over a wide area, it is advisable to use the longest tube which will comfortably fit inside the vivarium. Reflectors may be used to direct the beam further into the vivarium and increase the effective output, for species with higher UVB requirements."
About compact/coiled:
"UVB compact fluorescent lamps also produce diffuse, low levels of UVB at basking distances. However, at close range and/or if reflectors are used, the light and UVB may be intense, making good positioning difficult. These lamps decay more rapidly than tubes and may need replacement after six months.
A few brands of fluorescent lamps for reptiles, both compact and tube types, have been found to emit hazardous shortwave UVB. These have caused eye problems such as photokeratoconjunctivitis. Some manufacturers that experienced the problem say they have addressed the issue, while others are still addressing it. However, if your reptile develops swollen eyes or refuses to open them shortly after a new lamp is installed, see your herp veterinarian immediately. You may wish to refer him or her to this article. Lamp placement, the lamp itself and/or other factors could be responsible."
About Mercury Vapor:
"Mercury vapor lamps vary in quality and UVB output. These lamps also produce significant heat, and they cannot be thermostatically controlled, so they are most suitable for large enclosures. Be sure to follow the manufacturer’s guidelines and instructions for proper lamp placement and distances. Several mercury-vapor-lamp types are available. Inexpensive spot lamps with clear-glass faces may produce extremely narrow, hazardous beams of intense UV light and are best avoided. Flood lamps have much wider beams, and they are ideal for reptiles that naturally bask in the sun. They create directly below the lamp a zone of bright light and UVB resembling a small patch of sunlight. Brands vary in their UV Index. Recordings range from about 2.0 (full tropical sun before 8:30 a.m.) to 7.0 (full tropical sun between 9 a.m. and 10 a.m.) within the basking area"
Quotes From:
"FRANCES M. BAINES, M.A., VetMB, MRCVS, is a veterinarian researching the requirements of reptiles for visible and ultraviolet light. She writes on uvguide.co.uk and, with colleague Andrew Beveridge, independently assesses reptile lamps worldwide. She is currently an advisor to the Reptile and Amphibian Working Group of the British and Irish Association of Zoos and Aquariums."
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