Don't stress, jacks will eat anything meaty. Give it a day or two to settle. Don't bother with the bloodworms, too messy and small. Try chopped prawn or fish fillet, if it is hungry it will eat it, even in the wild baby jacks will mob chopped prawn. If it still hasn't eaten after a week go some feeders but it is better and cheaper if you can wean it off them ASAP. If you do end up with feeders try get feeder shrimp rather than fire gudgeons or whatever they use in sydney. I sold a heap of jacks recently about that size, my mates is eating chopped prawn and fish and gets feeder shrimp as a treat. Another friend already has his taking pellets, he used baby oscars to train it. Amehel0 took one as well, not sure what he's got it eating but.