The AquaFill electronic water level controller is designed to fail in the open position, meaning that the 24-volt circuit to the solenoid is interrupted causing the solenoid that supplies the water to become non-operational. It is truly a “Fail-Safe” system, so consequently, the AquaFill is used by koi farms and breeders worldwide. The AquaFill’s only competition is the auto fill, which uses probes to sense the water level through conductivity. It requires an elaborate, electronic circuit board to accomplish this. Because of the many electrical component parts, there are many things that can go wrong with it and does.