How do i care for a goldfish?

i have a stand that holds my 10 gallon tank and my stand has a second shelf that can hold a 5 gallon tank. my real question is can a goldfish live in a 5 gallon tank with a filter and aerator, gravel and ornaments? if they can, what types of goldfish can live in a 5 gallon tank? and also i was wondering if i could keep more than 1 goldfish in there. OR, if goldfish can't live in a 5 gallon tank what other types of fish [besides bettas] can live in a 5 gallon tank? thanks guys, all answers will help!