I might have to try this at my barn...I live in Louisiana, will the water get too hot and kill them? We use white plastic 50 gallon drum type things (yes that is the technical term, hehe).
Goldfish are for eating mosquitos, not "cleaning" the tank, which a lot of people seem to think lol that being said, we don't feed ours. We have them in all the stock tanks for the cows. Ours have always done really well. The only time they die is if the automatic waterer freezes and then the tank freezes before we catch it in time and the cows tip the tank over.