Ok, he didn't eat today, but he stuffed himself full during the last feeding. If you've ever seen an oscar eat so much that food is hanging out of it's mouth and it's gasping, that's what it looks like.
Could he have tried to eat too big of a piece of shrimp during the last feeding and injure himself?
Could he have tried to eat too big of a piece of shrimp during the last feeding and injure himself?