I have a length of thin acrylic tubing with fishing line going through it that I use as a feeding stick. What I did with my radiata, which was essentially the same size of that antennata, was to get some live ghost or marine shrimp, skewer them on the fishing line, and present them to the lion. This way he learned that the fishing line meant food. After a few days of that, I got some PE mysis, thawed it on a saucer, added some tank water so that I could separate the individual mysis shrimp out, then carefully found ones that could be speared on the end of the fishing line while remaining intact. The radiata has been eating those without any problem.
Right now I am trying to find something other than PE mysis and live ghost shrimp that I can feed him. He doesn't look like he wants anything that doesn't look like a shrimp. I did get him to eat a shred of silverside once, and he gave me a look of 'You tricked me', and he hasn't eaten any since.