Sorry I saw 29l and thought you meant liter. That will be more than fine. The uth's are labeled for tank size. You can use foil tape to apply so you can remove later. I have not seen one with a built in thermostat. You can get a thermostat right next to the uth in the pet store or use a rheostat (dimmer switch). As far as brands go people go back and forth on that. It kinda depends what you are willing to spend.