My betta had the same problem. I brought him home - he was eating fine, then suddenly he started spitting his food back out as if he couldn't swallow them properly which I know is not true. I got concerned when he refused for a week straight and started looking very aneroxic. OFL suggested I lace them with garlic but he still refused it. So I sucked it up and gave him what I should have tempted him with in the first place which is bloodworms.
I used freeze-dried bloodworms to tempt him to eat and after about a week of a purely bloodworm diet, I incorporated a pellet or two of pellet food with a small helping of bloodworms and he ate it fine. Start slow, and trick him into eating it.
1 months+ later I'm purely feeding him pellets, but I also give him some freeze-dried bloodworms 15% of the time, so once or twice a week as a treat. 2 feedings, 2 pellets each or sometimes I'd do a bloodworm and a half + 1 pellet every feeding. Flakes tend to cloud the water and require a little more diligence with water changes, so you might want to mix it up and keep trying with the pellets if that's something of concern. It's not a big deal, but if the betta is for a 13 year old girl it really is a good idea to wean him off the flakes. I owned betta when I was around that age or younger and I was very diligent with water changes because the container was very small and easy to handle. My dad showed me how to catch him without hurting him and moving him to a bowl so I can wash out his 3/4ths quart container. He lived on for about 3 years. Teach her how to do the same and don't give her a very intricate tank to clean or else it might be discouraging and time consuming for her.
It's not something of concern if he has an appetite and is acting fine. It might be stress (being in a new environment and so on) and it could be water temperature (the coldest it should ever get is lukewarm to the touch).
Last edited by Behati; 10-18-2011 at 02:55 PM.