Alan, I like to put 1 goldfish per 10 gallons of water. I recently had a die off of some goldfish I had for 6 years. I didn't cycle my tank on schedule and I built up enough ammonia to kill a couple. However, the largest fish, Goldy "The Legend" survived as he has the strongest immune system. He is 9 years old now. I rescued him from my nephew's tank when he was dying when my nephew was 7. My nephew is 16 now. Goldy actually learned to come to the surface to feed. Which many goldfish do not because they can suck in too much air at the surface while feeding. I am cycling my tank regularly once a week now even if the water appears clear. Another fish was near death when the others were dying but I brought it brought it back from the dead. It swims faster than I did before which really makes me wonder about that "That doesn't kill you, makes you stronger."