Cobra's are removeable; that's what I use. You can use regular tape to fix them on the bottom of your tank. The UTH the Bean Farm sells are exactly the same as the Cobras (same company), but might be a little cheaper for you. They are also great UTH, and I've never had a problem with mine.
HTH,
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Jeannie
0.0.1 California King Snake (Rex)
1.0 Mexican Rosy Boa (Lucas)
0.1 Baja de L.A. Rosy Boa (Bella)
0.1 Okeetee Corn Snake (Bess)
1.1 Rubber Boas (Isaiah & Esther)
0.0.1 Hermann's Tortoise (Moxie)
2.0 DSH Cats (Amos & Silas)
1.0 English Springer Spaniel (Jimmy)
and...
2.0 Kids
1.0 Husband