most silvers i've had or seen are semi-aggressive...so i'd go with semi-aggressive to non-aggressive fish...mine get along with 2 RTGG, 1 CK, 1 TSN, and 1 p.Bass, all ruffely the same size or with in an inch of each other...but nothing that can fit in its mouth...i'd say another silver, but i've seen alot of aggression when multiple silver are in one tank...depends on the temperment of you aro