by silver sharks do you mkean bala sharks?if so,your tank is to small. they need tanks that are at least 120 gallons(i think). they reach a foot long and are active schoolers.apat from that and the other schoolers(an issue bruinsbro already addressed),a betta would probably work,depending on whether gold barbs are known fin nippers
nearly a year of complete inactivity and still over 4 posts per day. dedication, eh?