The mercury vapor bulbs are great, and should give you enough heat. I wouldn't use them in a clamp lamp, though. They are notorious for failing, and the companies that make them recommend that they hang straight down, and not be moved around. The ZooMed hanging lamp stand works really well with them, and then you can adjust the height if you need to.
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Sohni
Northern California
0.1 Baja de L.A. Rosy Boa
0.1 Okeetee Corn Snake
1.1 Rubber Boas
1.0 Leopard Gecko
0.0.2 Hermann's Tortoises
plus my kids' herps:
0.0.1 California King Snake
1.0 Mexican Rosy Boa
0.1 Leopard Gecko