Wild idea -- skirts & a propane flame box underneath?

That's the ticket!! Not cats -- some nice warm skunks and raccoons and possums. I could just smear peanut butter on the bottom of my fresh water tank in the evening, and all night long the forest critters would keep the tank nice and warm. By the morning, the peanut butter is gone, and no more animals.

I knew this forum would come up with the perfect solution. Thanks, folks!!