I bought feeder goldfish to put into our pond that my husband built out in the backyard about 7 years ago. (couldn't afford Koi at the time) They all survived and each are now going on 12 inches long! I bring them inside each winter and put them back in the pond in the summer. I've heard that these fish can live 50 years or more in good conditions. So like everyone else has already said, I guess it just depends on the fish and how well they are kept.