I have a Hydrofarm on each tank, and I haven't been impressed either.

I don't think the fluctuations are good for them. Been toying with the idea (gasp!!) of removing the T-stats. Originally I had the Ultratherm taped to a tile beneath the tank, not the tank itself, and elevated the tank to where the glass registered a good temp via temp gun.

(I wouldn't risk it for a ball or a boa, but colubrids are better at recognizing and avoiding dangerously hot temps.)