I have an old set of real wood shelves, I want to make a quick set of cages out of.
Can I put the flex on the bottom of a ceramic tile and set this in the cage on the wood shelf and silicone around it to make it water tight?

Also I would add some washers giving it a small air space..Would this be safe?

Ive read a few older sites about cage building and they put the flexwatt directly taped into the cage with the substrate over it.