Having a lightbulb will help, but fire-bellies don't require UVB. For a setup, fire belly toads seem to like the half-land, half-water setup best. To achieve that, you can just buy a lot of gravel (big enough so they can't swallow it), make a slope so half of the gravel is higher than your chosen water level, and put moss on top of the dry area. That way, you don't have to use silicone to divide the tank and you can still have an ideal setup. Also, the slope will help your frogs climb out of the water.