We have something called Eco Earth, its a loose coconut fiber substrate. Almost like a mulch but like I said he has only had this issue one time with mealworms. Never with the crickets
We feed him crickets and only treat him with mealworms. It was just a few minutes after he ate them. We've only had him for a week and he seems to be doing well. He has adjusted well with us and will climb right into our hands when we go to take him out. He hasn't done it again since or done it...