A lot of terrarium animals thirst for the sun and, in addition to the heat, need the UV radiation found in sunlight. And while there are many terrarium lamps which promise UV, very few actually deliver it. It is true that such products as special fluorescent tubes for desert animals emit UV radiation, but unfortunately this is rarely in a sufficient amount and with increasing distance between animal and tube it decreases significantly. Thus, the UVA value of a JBL Solar T8 tube (30 W) for desert animals with 0.12 mW/cm2 at a 30 cm distance is equal to that of a JBL UV spotlight (100 W) at a distance of 70 cm. From a distance of 50 cm the UVB value is NO LONGER measurable!
A good UV spotlight, such as the JBL UV-Spot plus (100 W) continues to provide three times the UVB quantity at a distance of 100 cm, as a good tube at a distance of 20 cm. IF there is a pane of glass between the lamp and the animal, this halves all the UV values, because glass absorbs 50% of the UV radiation (JBL measurements at the University of Ulm).