Just quickly ..
Personally , I'd suggest no higher than 28C / 80F for the warm side .. cool side maybe 21C/ 70F ..
My Corn snake certainly prefers to be cooler than some recommended heat levels I've seen around .
I'm presuming that your setup is as required .... Thermostat regulating the heat source , suitable thermometer not one of those useless stick on ones , correct temps on warm and cool side , two identical hides ..etc
Latest info I've seen , suggests that nutritionally mice and rats are almost identical . It's just more convenient to feed one rat than multiple mice ...
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