There's really nothing you can do. It's up to him!
My clown ate a piece of stiff red algae one time, and it got lodged sideways in his mouth. After a day, it went in his mouth a little more, but was still sticking out. Looked like he was smoking a cigarette. After a couple more days, it was eventually gone. Don't know if he spit it back out finally, or it just worked its way "through the system", but he's still alive and well. (And doesn't eat stiff algae anymore!)