the sensor will output a specific voltage
you can connect a relay that will activate at a specific voltage off of the sensor circuit.
use something like this to control the pump (comparator relay control circuit)
LM393 DC 12V 2Bit Voltage Comparator Relay Control Circuit Module
compare a reference voltage vs the voltage reading from the sensor. if the sensor is higher, relay turns on the pump
when the voltage drops because temps drop the relay turns off.
EDIT:
that board is overkill for you use case, you could probably create this circuit from scratch, but I'm not good enough with this electrical stuff to know how.