Sounds like you have a 10~15 gallon aquarium. Yes, this is considered a small tank. The rule of thumb that I've often heard is every 30 square inch of the surface area of the aquarium for every inch of goldfish. Following that rule, your aquarium should be able to support total of about 10 inches of goldfish which you can divide among any number of fish you'd like (although I would never keep a 10 inch fish in a 10 gallon tank... that's just cruel). Mind you, this is only a suggestion and a well filtered, well aerified, and well maintained aquarium should be able to support more goldfish. Only thing is a small tank will stunt the growth of the goldfish. If your fish is over 6 months old, I would suggest getting a bigger tank.

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