I know this is an old post, but I just wanted to clear some stuff up. I'm no expert, but I have been a betta fish keeper my entire life. All these comments ARE correct to an extent. You CAN feed betta SMALL amounts of pea to help it with constipation; HOWEVER, you should NOT do it OFTEN. It is something you try, and if it doesn't help your fish, DO NOT JUST KEEP GIVING IT PEAS. They ARE carnivores, so they do struggle, but they eat all types of things in the wild so they can digest them; it's just difficult, so they shouldn't receive them regularly. My recommendation is to buy FROZEN peas, let one or two thaw or blanch them quickly for maybe a minute, and place them in a container of water immediately after. Peel the skin off the pea and take very small amounts on a chopstick, get your betta's attention, and pretty much hand-feed them that little bit of pea. Then, after they've consumed a small amount of ONE PEA, begin a fast for 3-5 days. Important note remove any pea that floats away or to the bottom; you want to see what of the pea your betta eats, which should only be about the size of a betta pellet amount-wise. I've done this for many bettas, and they have all done wonders with this method. Also, remember that most betta food says to feed them 2-3 times a day, which is very wrong. Unless you're very carefully feeding your betta, maybe one pellet at a time, and watching it eat, you should only put a small amount of food, 2 pellets, or a very small amount of flake, watch it eat them, then remove what it doesn't eat like every other day or even 4-5 out of 7 days a week.