The black light gives off NO UVB at all. As suggested, please get the Repti-Sun 10.0 strip fluorescent to help prevent metabolic bone disease and other health issues. They do much better with bright white bulbs and you can even use a standard household light bulb to help get the right temps on both basking & cool sides. Also, make sure you're using either an infrared temperature gun or digital thermometer with a long wire & probe end to check the temps as those are the only 2 ways to get accurate readings. Any type of stick on thermometer, round gauge (dial) or digital strip can be off as much as 20 degrees.