Yeah your aros won't be show fish if you house them together and their fins and scales might even look beat up at times but silvers usually don't kill eachother just nip and bite it's my interpretation black or "blue" arowana are the most peaceful when housed together even over silver arowana so you might wanna try one of those if you can find one as they can be mixed with a silver and don't seem to get quite as large, jardini on the other hand are a definite red flag when it comes to housing with tankmates if you try to keep two of these together your gonna end up with a fish dead or seriously injured!!! I've seen them kept with silvers and other fish if the other fish are much larger but even then the jar might snap and murder some of its tank mates. Also 300 is pretty big and I'd say you could keep these guys together in a tank that size but in a 125 1 aro is max and if they're 3-4ft monsters Id say even a 300 gallon tank isn't large enough for 2 sharing the same swimming space, you'd really need a pond for that, I'd try a clown knife or maybe a cool cat for your tank or some larger cichlids would be nice!
Oh and for his or her refusing to eat I gotta ask have you tried any live or frozen foods? Sometimes fish can be picky or just fast themselves at times I know my small jar has his days where he doesn't want his pellets so I have to drop in cut up dinner table shrimp or some bloodworms he always takes those, I think it's the smell maybe it's worth a try!!! Shrimp is a definite favorite of my arowana. Just let me know!! If he still won't bite you might have to feed live foods which is a pain.
