I like yor set up.
Just, I should add plants and/or barks in the substrate part.

A heater for the water is a good idea. 25W should be sufficient and then you can spend less watts !

You should have to hide it so that the frog doesn't get in touch with it.

I had a budgett frog formerly and I heated it's water set up tank with a 25W heater which was perfect.