I just went thru the same thing last week. Don't panic just yet, clean out the bottom of the tank completely, plants and all. If they are live plants, just put them in a container for now.
Feed him normally, but keep an eye on him and watch for the gravel in his poop. If he stops eating, becomes lethargic, or shows signs of anxiety, he may be in trouble......get him to a vet.
Beaker (just over 6" SCL) ate this rock:
But she passed it two days later.
Good luck.