stomach bulge

Curious if anyone has experience or knowledge in regard to this topic, thank you ahead of time. 1. Do they digest at the same rate we do? 2. If they are still full/stomach bulge after 8+ hours, did they overeat? 3. Does age/raw tilapia vs. pellets play a factor in their digestion rate?

Is this normal or a sign of overfeeding? It disappears after they poo a day later or so. I'm not sure if the "stomach bulge" while feeding is an overall swelling of the body that already happened before the multiple bulges happen?