Well, mine will eat when he is hungry, but, when he isn't, will spit quite a bit out through his mouth or expel out the gills.
Also, when he really isn't hungry, he will ignore the pellet when I put it in and still beg thinking that will work at getting him a piece of krill or a cube of bloodworms.
I have learned to only give bloodworms (frozen) after a water change, for now he expects it, and there is no sulking once it is complete, he just starts begging, sometimes as it is still filling back up. Much easier on me, since I don't have to see him act scared or pouty for extended periods of time.
I try to give krill (freeze dried) after taking pictures, this way he knows that when he is aggravated by this weird box that sometimes flashes bright light in his eyes, he will be given a treat afterwards. It seems to reduce the stress of the picture session when he knows he gets something in return for my bothering him in the end.
I use their greed and appetite to my advantage
I also feed Hikari ... exclusively.
I am about to go through a hard battle of wills with my O. I am switching him from Large Hikari Cichlid Gold pellets to the Medium Hikari Cichlid Bio-Gold+. He doesn't care for the smaller pellets, but they contain nearly double the vitamin content, and can be bought online cheaper than the Cichlid Gold in the store. I will have to be stronger and more patient than he is in a week or two once the large pellets are extinguished.