I have no idea what worms thoseare for a gecko haha, but i suppose it wouldnt hurt to try one maybe.
With him being already 8" it might be hard to add other large fish in with him, especially other Jacks due to his size already. If you could get a pair to form, it would be good in a tank that size. However, due to his size it might be hard. The best way i found, because i had the same problem with my Jack when i wanted to get a pair, mine was already about 5" at the time. I bought threeyoung females and placed them in the tank with him, but created a divider that the young females could swim freely through, but the male was to big to get through. It seemed to work, albeit i have said previously that my Jack was rather timid, which certainly helped. Once my male 'chose' a female i removed and sold the other two. It was obvious which one he picked because it was the only one left looking perfect, and the only one allowed near him.
Alternatively you could add other fish if you wanted, using a similar technique. Just be carefull. Stocking your tank is entirely how you see appropriate, but a breeding pair of anyfish always trumps a group of others IMO.
As for moving the article, a mod will do this if they come into the thread and see this.
James