You NEED to be able to control the heat inside of the incubator, that is all that really matters since usually the humidity in your tub will be self contained (none can be lost or gained) however many like to make sure the humidity is right in the incubator as well as a backup. If you can afford it pick up a Helix or Herpstat as well as flexwatt and a fan (to better regulate the temperature inside of the incubator, the more circulation the better). The more failsafes you put in, the better off you are.