Hey guys, I was interested in a little advice.

As you all know, I am not fond of using CHE's or Red Bulbs ... only because of humidity issues and because such things can, under certain circumstances become fire hazards when two feral cats enter the equation.

From the very beginning the terrariums that house my ball python and my red-tail boa have been heated by Two Zoo-Med under-tank heaters, mounted on the sides of the terrarium in the far-left, rear corner, one on each pane of glass. This has worked out well, yielding highs in the low 90's (93 degrees, max) and an ambient air temperature on the hot side of 83, and 79/80 on the cool side. I cover most of the screen top with a trash bag. My humidity stays at a solid 60% in both terrariums.

I have concerns, most notably, am I putting the animals at risk for burns with the heat pads mounted on the sides like that?

What I'd rather do, is mount one Exo-Terra heater, under the tank on each terrarium instead.

For substrate, I begin by pouring a quarter inch or so of Desert Blend (crushed walnut shells) into the terrarium, and then I layer about an inch of aspen bedding on top. My boa likes to burrow, and my ball likes to snuggle down real deep into it and coil up when he's in his hidebox.

Now, if I mount the Exo-Terra under the tank, will I get a slight increase in heat (because the substrate in conducting more heat) and will my snakes still be able to burrow down into the substrate without being in danger of getting burned? I was considering covering the glass directly above the UTH with a piece of cardboard, and then putting the substrate on top, but I was worried of another fire risk.

If you have any advice, I'd greatly appreciate it, as always.

Thank you