Thanks for the response. How much of a gap would you recommend for proper ventilation? (Most tutorials don't mention spacers at all, or they like their tubs snug on the shelf, so I'm kind of confused.) I just don't want my animals escaping somehow or being tempted to try and escape, thereby damaging their noses.

If all of the species in the rack like their hot side around 90, would the issue be them... smelling each other? I already have multiple species in a room together. Obviously not in such close proximity, but I'm surprised they'd care?