They don't usually carry it long-term, but if he's constantly inhaling the same amount of food, there will be some left over as he digests!
You may want to try cutting back to feeding once every other day, or even every three days to see if the bloating goes down. If it doesn't there may be another problem, such as a blockage, that needs addressed. Like I said though, the Glofish I once had and the ones we have at the store I work at are often very large in the belly area