Studies by hobbyists and scientists alike have shown that series of fluorescent bulbs are superior to most other models and accurately reflect their intended use. The highest UVB levels are found within 6 inches of the bulb, and output declines by 80-90% at 18 inches from the bulb. Because of this, basking sites should be located relatively close to the light source- ideally, for any reptile that actively climbs there should be a series of perches or basking areas at various distances from the heat and UV source.
What UVB Bulb do I need for my pet reptile or amphibian
By far the most widely used and accessible type of UV bulb or lamp is the fluorescent tube. Just like natural sunlight, these tubes need to be set up and used responsibly in order to provide your iguana with the life-sustaining amount of UVB it needs to live a long, happy and healthy life. Several brands of fluorescent UVB lights are available, but not all brands are of equal quality. The Green Iguana Society recommends the ZooMed Iguana Light 5.0 (also called Reptisun 5.0). This bulb has been on the market for some time and has been shown through studies to provide large enough amounts of UV light to keep your iguana healthy. We recommend that you mount two ZooMed 5.0 bulbs in a high-quality fluorescent fixture to get the best results. Ordinary "full-spectrum" fluorescent bulbs (such as plant-grow bulbs) do not produce adequate amounts UVB! Only bulbs especially made for reptiles do. When selecting a fluorescent lighting solution, please be sure to choose one that is specifically made for basking reptiles and all is rated for high UVB emissions.
Lighting and heating for reptiles: They are not the same thing
Not all reptiles and amphibians require the same amount of UVB to be healthy. Exposure to sunlight will vary greatly depending on species, their natural environment, and their habits in the wild. Many species of reptiles and amphibians are nocturnal or live in burrows or on the floor of the rainforest, such as crested geckos, leopard geckos, or poison dart frogs, and are not exposed to significant levels of UVB in the wild. For these species, low levels of UVB, such as 2.0 bulbs, (or none at all!) are sufficient. Some species, such as many chameleons, live in forests, where much of the sunlight is absorbed by foliage. For these species, a moderate level of UVB, such as a 5.0 bulb, is appropriate. At the opposite end of the spectrum, there are reptiles that thrive in full sun environments, such as deserts. Common pet lizards such as bearded dragons and uromastyx thrive under intense UVB expose from 10.0 or Mercury Vapor Bulbs.
They do not produce any ultraviolet B wavelengths