Anyone who has owned a Betta fish has likely experienced, to one degree or another, a Betta fish that just won't eat no matter what you do. This can be for a number of reasons, most of which I'll get to in a minute, but if this is your first Betta and he's just getting adjusted to his new home (for example he was brought home less than a week ago) the explanations are usually pretty harmless. If, however, your Betta was eating fine before and then suddenly started refusing food he once ate without question, you may have a more serious matter on your hands. Below we'll take a look at exactly what both situations entail and what you should do if you think you have reason to worry.For Brand New Betta Owners: If your pet has just newly moved into your home from a pet store or breeder and isn't eating, start here (if your pet is not new, you may find it more useful to just skip to the next section).
When a Betta is first brought home, it not only is faced with a lot of immediate stress, but also is often being offered a food that is different than whatever the pet store was feeding him (or her), both of which can lead to a loss of appetite. When I brought home my first Betta fish, it wouldn't eat for almost a WEEK, and I was getting really worried. Eventually however, he gave in and started eating the pellets I had bought, and lived a happy, long life thereafter. However, if after a week or so your fish still isn't eating, consider trying a different food just in case (but don't freak out too much, as it takes several weeks for a Betta fish to starve, they have very efficient metabolisms).
Also, if you are using pellets, a fish who is used to flakes might find the hard, thick pellets tough to handle. If you soak these in a cup of water for a minute to soften them up they may go down easier and you can ween your fish onto them this way.
For Bettas Who Suddenly Stop Eating: Alright, so if your Betta fish won't eat after weeks, months, or even years of happily chowing down, it's time to do some problem solving. First of all, has anything changed lately? A new food being introduced, a tank being moved to a new location, etc, might be affecting your pet.
If nothing is coming to mind, then the most likely cause is that your Betta is either sick or constipated, both of which can be deadly. First things first, you'll want to check for commons color changes, lethargy, spots or bumps, and fin or scale deterioration that would indicate a Betta fish disease might be at work. If you aren't seeing anything, then you're in luck because constipation caught early is easy to help your fish survive and you can be back on track soon.
Curing Constipation: Betta fish are extremely susceptible to over feeding, so constipation isn't rare by any means. The easiest way to cure this is to encourage your Betta to eat something that will act as a natural laxative. The easiest one is a frozen pea: Simply take one pea and microwave it in a small dish of water for 20 seconds or so. Then remove the pea, and peel off the outer skin. Then cut up the inner pea into little pieces and offer this to your Betta (usually the unique color will intrigue him enough to take a bite even if he's been refusing normal food). Feed him a couple small pieces and then wait for a couple days and things should take care of themselves.