I picked up 3 Comet Goldfish today. Not to be used as food, but for testing my new aquarium.

I noticed today the salesperson said that you should wet the food before adding to the tank, because if the fish try to eat it on the surface there is a good chance they will swallow air and then die.

I don't remember doing this growing up as a kid, and I never seemed to have a problem. I'm wondering if this is paranoia, or are comets a little more risky than other fish?