Commons can grow quite large!!!! A 1 1/2 gallon container is not even suitable for 1, IMO!!!!!
That would be very cruel to have common goldfish in anything smaller than 20 gallons. If you don't have room for anything larger than a fish bowl then consider a betta instead!
I agree! GF bowls are NOT for GF! They can be used for bettas only! GF realease a growth hormone in their water and if there is not enough water and filtration to dilute that hormone, then the fish will become stunted and not live to its full potential. Please, if you want your fish to be healthy and grow to their potential, then get an aquarium and not a 5g, either! Comets and commons need at least 15-20g each.