The truth is, there aren't a lot of people out there willing to front
money up to do actual studies on fish. It's up to us to do our own
research and talk to as many sources as possible. You have to listen to
advice and decide if it fits into "common sense" or "mere speculation"
categories.

For instance, if someone says to you, "a betta's food portion should be
about the size of one of their eyeballs". They had better darn well
tell you why. Without an explanation, it might as well be fiction.
"Because I've done it that way for 22 years" is not an answer by
itself. When someone offers advice, just be sure to have them explain
why and trust your gut.

By the way, bettas have a relatively short digestive track and their
stomach is about the same size as one of their eyeballs. Feeding this
amount helps to gauge safely so that food can pass and not block up
inside the fish.