I microwave a large cup of water for about a minute and submerge a ziplock bag with the mouse inside. I wait a while for it to completely thaw, but it's definitely not hot when I put the mouse in the cage. Thanks for that link. I started him out in a tub that the store put together for me, and moved him into a glass tank recently. He has eaten mice in that tank but I was told a heat lamp wasn't necessary with a UTH.