Bettas are carnivores and require food that is high in protein. There are many food options for bettas – flakes, pellets, freeze-dried, frozen, live, and in gel. The best diet for a betta is one that contains a variety of foods. Try alternating between a few different food sources for different meals.
A betta should be fed every day! One meal per day is adequate, but two smaller meals are even better. Always be sure to promptly remove any uneaten food from the tank because as the food decays it raises toxic Ammonia in the tank.
It is not uncommon if your new betta does not eat at first. He or she is adjusting to their new environment and it may take a few days to settle in. Keep trying to provide food and scoop it out within a few minutes if uneaten. Eventually, when your betta gets hungry enough, they will eat what you provide them. Offering a few different options may be a wise idea to see if something in particular appeals to them. Be careful not to offer too many choices at first though, as if they realize there may be an endless trail of different foods they may choose to wait and see what comes next. Contacting the store where you purchased the betta and inquiring about what they were previously fed may also help for you to determine what they will eat.
A full-grown betta’s stomach is approximately the size of his or her eyeball. Please keep in mind this is a general estimate as different bettas may require different amounts of food based on their age, size, etc. A little food goes a long way, so be careful not to overfeed! Bettas, just like people, can develop constipation from too much food or lack of variety in the diet. Some betta owners choose to fast (not feed) their betta one day per week to clean out their system and prevent constipation. Additionally, soaking dried foods, such as pellets in dechlorinated water for 5-10 minutes will prevent the food from expanding once inside the fish, helping to prevent food-related illness.