
I recently got a new female betta (that red mark in the bottom left) and for several days she would refuse to eat anything I put in the tank. She didn't want brine shrimp, pellets, bloodworms, flakes, etc. At first I figured it was because she had just been fed when I bought her so she wasn't hungry, but it went on for several days.
Fast forward to yesterday where I'm still trying to feed her and she repeatedly notices and then ignores pellets sinking past her, except this time I watch her behavior a little longer and I see that she circles back to the pellet and picks it off the sand and eats it. I drop another pellet in and she does the same thing.
Turns out for whatever reason she'll only eat food that she finds on the bottom of her tank and doesn't even make an effort to compete for falling pellets like my other two bettas do with their tankmates. So now every once in awhile I'll see her scrounging around the bottom of the tank with the pygmy cories looking for something to eat.