A thermostat monitors the temperature and turns the heat pad on and off to keep the temperature at the value you entered, like the one in your home that controls your heat or air conditioning. Most thermostats come with a probe. Inkbird is a brand we trust and they offer many different options for heat and humidity monitoring.
A rheostat or dimmer is a dial that allows the user to adjust the level of heat based on their preference but is not automated in anyway. It works like the volume knob in your car. Rheostats can be used with a thermostat but it’s not necessary.
