Many a time you have been to the lake, pond, or river and seen people throwing little bits of bread into the water. Yes, sometimes that is for the ducks, but they will miss some, and that can end up with the fish eating it. Or on the other hand, you may have seen fishers using bread as bait. That can often lead to people thinking it is ok to feed fish bread. However, can pet fish eat bread? That is a different question that we need to clear up.
In a word, no. Fish do not have the same digestive systems as humans and other mammals. They do not have the same robust digestive system that is exposed to many types of food. If you do feed your fish bread, you are asking for problems, and they can often lead to your fish dying. Bread is a human food that no animal in the wild can find, especially not fish. The yeast in the bread can bloat the stomachs of the fish and lead to huge problems such as being unable to swim properly.
Do not feed your pet fish bread!