My large one did before I traded it, he was about 13" or so. He ate smelt, shrimp, krill, MP and massivore deligth pellets.
I fed him every 2 days. He did went on a hunger strike one time for about a week. At that point, he was on MP only. I started to throw krill in there, he'd did the same thing (chew it and spit it out after a few seconds). I keep trying with scallops, and finally ate a piece of smelt.
How long was he on MP ?
Try to cut it smaller to where he can only swallow it, if not, try different variety.
He's propably just picky, if he's not healthy, he wouldn't go for the food in the first place
stan