Totaly depends on the temprament of the jag. i have seen 2" jag do major damage to to other cichlids so be careful.
if the arrowana was much bigger than the jag it may work.
You will need a bigger tank eventually to ensure relative harmony between the fish and space for the arrowana.
also if the jag is too small its gonna be dinner very quickly.
my old arrowana grew at 1 - 2" a month for the first 9 months then slowed to .5 - 1" after that but increased in bulk as well.
good choices for arrowana tankmates are:
ones ive tried
girraffe cats
barbs (tinfoil, lemon, spanner)
silver sharks
severum
Earth eaters.
tilapia. (not buttiferki)
clown knife (in a tropical pond)
Red tailed cat (in a tropical pond)