Koi Pond pump fails

Question
My neighbor recently lost most of her Koi fish due to the fact that maintenance workers overloaded the breaker that supplies power to the pump and did not notify her.
I want to create a simple circuit that would detect the loss of voltage at the breaker, then activate another circuit that would then turn on a siren and alert her of the power failure.
Do you know of any other way to prevent the loss of the fish in a case like this??  Just how sensitive are Koi fish to loss of circulated water.??

Answer
Hi,
I am sorry but I am not up on electrics so could not advise on a system that you are looking for, water is circulated in a koi pond so that the water can pass through a filter which is realy a necesity if you keep koi as the filter helps to keep the parameters of the water constant. so the answer is "if you keep koi you need a filter.
George.