That tub is also called a 9 1/4 gallon Iris. An UTH works just as good as Flexwatt. The only reason people use flexwatt is because of its flexibility (by flexible I don't mean it bends) in design applications. By that I mean no matter what kind of rack or cage you build, you can put flexwatt on it and then wire them together if need be. Your UTH with a thermostat or rheostat will work fine.