The new energy-saving compact flourescent bulbs that people are being encouraged to buy have a small amount of mercury in them as well. If they should break, I've read that to be safe, windows in the room should be opened for ventilation and the pieces should not just be swept up. As much of the bulb as possible should be put into a double plastic bag and that should be closed up. The bulb should not be disposed of in the regular trash, but should be disposed of at a place meant to handle this type of bulb.
I read that after a spent MVB bulb I had in the basement did break. I opened no windows and yes, I did sweep up the pieces. I did, however, triple bag the broken bulb and took it, along with another dead MVB, to hazardous waste to be disposed of. I'm still here

and for the one bulb I think the amount of mercury I was exposed to was minimal (still not good, though).
Handle the bulb carefully and don't let any water get splashed on it. For a 100-watt MVB, the general mfgr's distance is 12 inches from the basking turtle. If, however, you're going to hang it over the basking area in the pic above, I'd check and double-check the temp. The sides are going to contain some of the heat, which will push up the temp.
There is a limit on how high you can raise the lampstand safely. I'm using one with a stock tank that's on a pallet on the floor and the little amount of added height made adjusting the temp more difficult.
"You become responsible, forever, for what you have tamed." -Antoine de Saint Exupery-