Keep trying with the pellets - give him the meaty foods as a treat once in a while. If you are hand feeding him, it should be easy to get him to strike the first thing that drops in the water, and after a while he will accept the pellets. You'll be amazed at the improvement in coloration/health. Good luck!
Hikari Gold, Hikari Bio Gold, Hikari Massivor, Hikari food sticks for Arowana and omega one pellets and some shrimp.Mine loves all these foods and the Hikari really brings out his colours
I have found that Jags are probably the easiest fish (besides Oscars) to train on pellets, since they are always hungry. A week without food and they'll eat em right up. All my Jags are wild caught here in Florida.
In the wild they eat mostly fish, so I feed live fish at least once a week. I don't use goldfish, but it's easy for me since I can catch minnows, bluegill, and jewel cichlids all year round.
My Jags eat shrimp,beef heart, all kinds of worms, maggots, and almost anything that fits in their mouth. (Although sometimes they can gang up and go Piranha on an unsuspecting tankmate)
My biggest Jag is about 14" as well, and a 3 inch bluegill is nothing but a light lunch to him.
I feed mine, flake, bloodworms, earthworms, mealworms, tadpoles, baby frogs,crickets, ants, mosquito eaters and most anything I can find live. I have heard of people feeding moths to their fish as well. I havent tried moths yet.
Just be careful when feeding wild caught frogs and insects. Do some research. Make sure they are not poisonous. Make sure they are frogs too. There are alot of mildly poisonous toads.
My fish love the tadpoles especially and their growth rates have increased. I noticed since I started feeding the tadpoles and baby frogs they display more of their wild characteristics. And they have colored up nicely
When mine was smaller he readily ate Omega One, Bio Gold and Massivore and occasionaly jumbo krill and market shrimp. Now that he's getting to be a big boy the only pellet he'll eat is massivore and even that is kind of hit or miss.
It's very important to feed your fish with pellets. I recommend Hikary for the palatability and the high quality. Listen ... Hexamytha/HITH happens because lack of vitamins in the food. Beef heart, nightcrawlers, worms .. they don't have vitamins at least not enough to matter. Hikari contains lots of stabilized vit. C and that counteracts HITH. Do your fish a favor and try pellets or granules. He'll accept them cause every Jag is greedy. I have one and I know.