Jars are none for being extremely territorial and I think adding a second one would be a big no no, though many have found that the aggression doesn't come until around the 7-10" mark. So, though he might seem fine now, there is still a good chance that he may become striate evil and can kill a silver a few inches larger. You said your Jar got sucked up the filter and lost some scales? How do you know the wound on his belly is not also from that and not the silver? The silver should out grow him, and there is a good chance that this combo could work for you for a while. I would really really watch closely as the Jar hits the 7" mark onward though. Keep them well feed, and I too would recommend a pair or more of some type of dither fish. I personally use blue pearl gouramis, I think they're really nice looking and they are really fast and smart. So far my Jar (2)Pacus tsn and rtcxtsn have not been able to catch them(only been about a week but so far so good.) So I would say it's definitely possible, but remember theres a good chance that you could lose one also, it's just a risk you have to ask your self if your willing to take or not. Also check the Jardini tank mates sticky for more info. Best of luck and Keep us updated!