no speices what so ever could servive in a 12" wide tank until adult size--- jardini's get twice as long as the width on that tank and aren't very flexible, and silvers can get 3-4x that width. sorry no go.
You would need atleast a 180 to raise any aro to an adult size...but even that wouldn't be a long term tank. You're better off looking for something with a 2 foot width, minimum, and around 6 to 8 feet long.
For baby size like under 10" than it should be fine, you must upgrade though. Jar grow pretty fast so if it 4" i would say u got about 4-6 month till he outgrow the tank.