Thanks for the replies.
The rock trick sounds like a good choice, because I have noticed that Cocoa will eat out of the bowl until he has made a hole in the center of the food. Then he moves on to the next bowl, does the same and on to the next etc...
Not sure if the timed feeder would work for us, as Cocoa's brother Bandit is such a nibbler that I fear he would not eat enough. It's strange that two litter mate brothers can have such different eating patterns. Bandit barely maintains his weight at 12lbs. He will eat about 6 pieces at a time frequently throughout the day.

Emily, can you tell me what kind of treats have the Cosequin ingredients in them? I might like to give them a try, just to see if it benefits him any.

Thanks again,
Janet