I was feeding mine with thawed misyds and blood worms. I did not realize how large and fat they can get until I found a local source of black worms, he eats them until he can take no more and has gained a lot of weight, colors are brighter and the fins more translucid and clean.
It really worth the effort to find black worms from them. I buy enough for two weeks at a time and they can be easily kept in the fridge in a wide pan with 1/4" to 1/2" deep water, change their waterevery two days using RO/DI.
The average lift span of these fish in captivity is measured in MONTHS, not years. They just do not eat prepared foods. I have tried, done a bunch of research, and many have agreed, they are just really tough to keep in captivity. They are beautiful, so I completely understand, but these fish should not be kept in tanks. It's just a shame to keep a fish that you know will die in a few months of starvation. Sorry to be a buzz-kill, but please pass the word along. Best recommendation is to use some garlic to get him to eat, then have a good mix of Mysis, and Blood/black worms on hand. I even recommend some live brine shrimp.
