I am not that familiar with the ceramic heaters, I have never used one. I do have a question about placing it in the tank. I can see where more heat would be within the tank this way, but do they also cause humidity to fall like lights do?Inside the tank would be most energy efficient, but you will have to make sure your hermit crabs can't reach it,
Second question, if the 'covering' is glass, is there a chance that if one used waterfalls, misters, etc to boost humidity could the glass shatter if water hit it?
Reason I ask is a member on another site did put a light within her tank away from where the hermies could reach it. But it did dry some of the humidity and while attempting to boost the humidity hit the bulb and it shattered within the tank?