I'd wager that my plastic tub was a lot cheaper (and lighter) and not nearly as deep as a fish aquarium! And the styrofoam container I used as an outer insulator was free.
Originally Posted by nworth
In my case, the water pump was for either a large aquarium or a water fountain. The aquarium heaters have the issues discussed (and worked around) above. Personally, I think if you use a PID (which is accurate to .1 degree C) you're better off using a stronger heating element. But that's a personal preference. I have no idea how accurate the controller is in an aquarium heater, but I doubt it is as accurate as a PID controller. But it is probably good enough.