Bettas can be overweight or underweight without a proper diet. The Betta in this photo appears quite thin.
Q: Anon wrote,I feed my betta a combination of frozen bloodworms, Hikari Bio-Gold pellets and freeze-dried brine shrimp. Is he getting a balanced diet and also, can you recommend how much I should feed?
A: Yes, I think that in combination, you are feeding your betta a well balanced and nutritious diet. Hikari Bio-Gold alone is a balanced formula, but like you I feel Bettas can benefit from a variety of foods including frozen bloodworms and brine shrimp, which are closer to what they would be eating in nature. Dry foods like flakes, pellets and freeze-dried brine shrimp have a very low moisture content, around 6 – 10% and thus tend to suck up water like a sponge often expanding 2x – 3x their original size. For this reason, I find it can be beneficial to soak them is a container of tank water prior to feeding. Ten minutes is plenty of time and you will then be able to see the true size of the food particle. Determining how much to feed depends on the size of the food, size of the Betta and the Betta’s appetite. A general rule of thumb is that a Betta’s stomach is about as big as one of his eyeballs and should be fed that volume of food once or twice per day with one day of fasting each week. This equates to about 3 – 4 Bio-Gold pellets or about 4 bloodworms. Healthy Bettas tend to act ravenous, even after feeding, so it’s important not to fall for their theatrics and overfeed. Too much food or food that soaks up water in the Betta’s gut may swell and cause constipation or even Swim Bladder Disorder. Because I only feed my bettas once per day, I tend to be a little heavy handed on the feeding but I’m careful never to feed them to the point where they appear bloated. Bettas who have a less then enthusiastic appetite should be observed when eating and any food that goes uneaten within ten minutes should be removed so as not to foul the water. If nothing has been eaten, try again after a couple of hours.
Bettas can gain and loose weight too. If your Betta appears over or underweight, adjust your feeding regimen accordingly.
The Betta in this photo is a healthy size.