HCA: Hermit Crab Association

How bad is it for a UTH to touch the substrate? I ordered one off of reptile basics but got 11x23. After I ordered it I read how the heater should not touch the substrate. Well my tank is 12x30, so it will absolutely touch the substrate. How bad is this? Should I keep this heater or try and return it for the 6x23 size?

Not bad at all! You want to heat the air, so most of the 'air' space should be covered by the UTH (ie - if it doesn't cover the entire top to bottom, don't put it closer to the bottom). But nothing bad will happen if it goes below the level - there will not be hot 'pockets' and your crabs will not 'cook' to death like some might have you believe. The worst case is that the sand in that area will tend to dry out a bit faster. Just keep an eye on it and add more water to the sub as needed.

I was afraid it would dry their sub out. I have a 13in high tank and the heater will cover 11 of that. So I wasn't sure of that was too much

Some crabbers have the UTH go right from top to bottom. Just keep an eye on the sub in that area so you can add more water to it as needed.