Many choises for Silvers that is passed 12" mark...
Before 12", i have succesfully combined Severums, Silver dollars, Tinfoil barbs, Giant gouramis (should keep eye on them bcoz some individuals can became very aggressive)...
If given a big enough tank, it's possible to keep almost any fish out there with tankmates. Jags wouldn't be too aggressive in anything from 225 and up unless it's an individual that's unusually aggressive.