I would make the bowls alot smaller. The snakes don't need to soak in them, and if they do, you know they have a health problem(mites, too hot, not enough humidity, etc).

I like to use the 3" souffle dishes(or ramekins) that you can find at WalMart or Target. They are pretty inexpensive and sometimes you can find them at the dollar store. I also use these small stainless steel bowls with blue rubber coating on the bottom for some of the snakes. They are about $3.50 apiece but clean up very easily and don't create too much humidity. I use them in my 15qt tubs and the humidity is fine(50-55%).