Rheostat or thermostat

[aquaculture]

Which is better?

Also which is better to use with a human heating pad?

Which is better at maintaining a high temp of 88F and a low temp of 75F?

(I'm going to be using two different pads to maintain the low end temp and high end temp).

 

[aquaculture]

Okay, I figured that the thermostat doesn't need constant monitoring and is best.