And, I am guessing to much would be harmful, but what is to much according to a the reading. I use a reptiglo 5.0 48" linear for 2 chams I have in side by side cages (with a black, non see through barrier between them). I have had them for 8 months and seem to be doing real good. I just want to be sure and get a meter. Specially cause I want to be able to take them outside if it ever gets warm enough here in Utah, which for a few days of the summer it will.