I use the Finnex submersible titanium and PinPoint temperature controller. Love the Finnex's. Must be sure never to raise them while hot however, as the safety mechanisms indeed work and internal fuse will trip.
I agree with @CastAway very good heater, if you do not have a controller, you will have to get their controller. The company is in Chicago USA and you deal with people and not a call center. I did not have an issue just a question when I contacted them