They don't need any UVB at all if you supplement their diet with calcium+ d3. I would recommend just using a normal low wattage bulb that's not too bright. But if you really want a UVB bulb then use a 2.0 but still remember to supplement with calcium+d3. Also a UVB starts to emit less after about 6 months so its probably a good idea to change the bulb if you haven't already. Hope I helped.