The amount of UVB received also diminishes with distance. It is generally
recommended that any Repti Glo UVB tubes be no further than 12" (30 cm) away from
the subject. At greater distances than this, the amount of UVB actually received will be
minimal. For reptiles with very high UVB requirements, such as desert species, tubes
should be placed as close as 8-10" (20-25 cm) above the basking site. Tubes also have a
limited life and require changing at least every 12 months in order to guarantee continued
UVB output. Although there may be no visible deterioration in the performance of the
tube, the invisible UV content decays as the tube ages. It is a good idea to place a small
adhesive label near each fitting with the date the tube was last
changed clearly marked.