I hate to tell you this, but you can't keep goldfish in a bowl. To keep them humanely, you need at least a 5-gallon tank per fish, preferably more, with pumps and filters, the whole works.
Goldfish, when kept correctly, live to be at least 30 years old.
I found all this out when my kids brought home two fish from a carnival -- I too kept them in a glass bowl, and thought they would be happy with regular water changes. But when I started to do research on proper care, I learned that keeping them that way is cruel, akin to slowly torturing them to death.
How about a guinea pig?
P.
I was wondering if there were not larger issues and I'm very glad you responded.
We're not prepared to deal with a tank, so I won't be getting any goldfish. Thank you
for letting people know this. (But now you have to write to Elmo too!)
G.
Who said you can't keep goldfish in a bowl?