i have 1 big gold fish and 11 zebra danios. i think my gold fish is really old becauze it keeps stoping and going to sleep and i keep seing this 1 zebra danio (or more) biting his tail. are they playing around or is the zebra danio really hurting him?
They shouldn't be in the same aquarium for a start, danios are tropical fish, goldfish are cold water and don't appreciate warm water. Goldfish can live for 20 or more years. Danios for around 2-3 generally.
I agree with answer above, they should not be in a tank together. Although I had a goldfish with a giant danio live together for long time, and they were fine. But my room was also a pretty good in between temperature. But if your tropicals are fin nippers, I would definitely separate them. Also bear in mind that goldfish need A LOT of space. So if you have all of these in say a 10 gallon, then you've really got a problem. That would not be NEARLY enough room. Goldfish can live up to 60 years if well cared for. At least I know that the feeder ones can, as I never had much luck with fancies. I would get a separate tank to move your danios too, it sounds like they are chewing on your goldfish.
Perhaps they should not be together
