This is going to be a personal preference. The room my rack is in isn't kept warm and averages about 23°C so I have heat mats that cover half the bottom and goes up the sides of the tub aswell to keep the heat in the tub. This works perfectly for me but not for everyone so again it's going to be personal preference and will differ on everyone's situation.
When I first started I was told the rule of thumb in one third of the bottom of the tub to be covered with a heat mat which is great if your room is kept at a perfect temperature. Which mine is not lol
What you have should be fine but I'd probably go with a slightly smaller UTH. I also prefer Ultratherm UTHs over the Zoomed brand because they don't get as hot.
I always thought "reptile safe" heat mats are only called that because they are "safe" to go inside the enclosure and no there not safe to use without a thermostat.
According to Ultratherm their heat pads can be used without a thermostat but I wouldn't do it.
This is interesting but I don't know how they could guarantee anything without stipulating an ambient temperature unless the thing has some sort of built in thermostat.
Edit
Ok I looked it up. It says 90 to 95 degrees at an ?average? room temperature. It also says that if you want to be more accurate to use a thermostat. LOL
Last edited by JodanOrNoDan; 06-20-2016 at 03:40 PM.