1. Super Aggresive cichlids (like the Jag) are usually not recommended with Silver Arowanas.
2. Silver Arowanas need to kept alone till they are about 1ft in size before introducing tankmates
3. Besides the above two issues, a 7" Silver Aro will outgrow th 2" Jag and can eat the Jag (or at least try to).
I do have a Silver Aro and a Jag in the same tank or over a year without any issues. They started sharing a tank when the Silver Aro was about 1ft and the Jag was about 6". (Currently, the Aro is about 24" and the Jag is about 13-14")
Good luck,