Goldfish in a 30 gallon tank

Question
Someone gave ma a 30 gallon tank along with with a filter and a bubbler, and 9 comet goldfish at about 1 1/2 inches to 3 inches long.  The tenth fish is a catfish looking fish.They are doing really well.Can I add 2 more comets without disturbing the balance?

Answer
Adelaida,

    No, unfortunately you should not add any more fish to the tank. It is a bit over crowed as of now. Goldfish are very messy and produce a lot of waste that is then turned to ammonia. One goldfish should be housed in nothing smaller that a 20 gallon. With you having 9 of them, the tank should be a lot larger than what you have. If there is any way to get a larger tank, that is what I would say to do. If you cannot, them you might want to think about giving a few of them away. With the size of your aquarium the maximum amount of goldfish you can house and keep happy and healthy is one.