with a jag that size it is going to be hit and miss unfortunately especially if he has been in the tank on his own for any length of time. All my fish that are larger iv had together since juvenile and so far so good. Saying that tho iv just got a small jag that im hoping is male and a female that is quite a bit larger thta im hoping will go together when the male is a bit larger and bulked up a bit. the tank will be plenty big enough with plenty of hiding spaces so he can get away if needs be, a spare tank he can go in if things go really wrong and im prepared that one of these might always have to be on there own, but it might work out well and i might get some fry. You never no for sure, its all trial and error just have a back up plan. Iv seen some real oddball tanks with things together that you never thought would work and there really peacefull tanks