Fractional charge and automatic U(1) symmetry without domain walls

All fermion representations compatible with fractional charge in asymptotically free SU(N) gauge theories are constructed. With a survival hypothesis argument it is shown that none of them have three light ordinary fermion families. Automatic U(1) symmetry is constructed for each case, but all of them are plagued with domain-wall problems, unresolvable by the Lazarides and Shafi method.