your moms tank is 6 gallons. she can NOT keep six fish. evidence the fact that they're dieing.My mom's in the smaller tank!! She can only keep 6 fish.
unfortunately a great many shops don't know anything at all about the fish they sell. you came here seeking advice and are rejecting the advice you're being given.we were told by 2 different pet shops. They said my tank can house 10 and hers 6.