I don't know the best type bulb but it needs to be UVB, or UVA and B. "Grow lights" are often just UVA (but I'd fact check that. Anyone???) I think about the right level of light is sold as bulbs in pet stores for "tropical" animals. It's less harsh than the "desert" type. As far as I know, "desert" might be acceptable as well because these are toads not tree frogs, but I suspect tropical would be better since they spend a lot of the day hibernating.

Anyone have information on actual wattage numbers or bulbs?