Okay I know synthsis jsut advised against peas... I will address that on the forum. Think of them as an ex-lax chocolate: Extremely tasty, but only to be used for medical purposes! You can use daphnia as well, but I know it is hard to find sometimes and it is too small for my betta to eat. Here is how you go about treating constipation with peas:
1) Source out a frozen pea. Don't use canned, they have lots of salt and preservatives.
2) Thaw it (I run it under warm water).
3) Peel the skin off (Just rip open the skin with your fingernails and pop the pea out. It's easier than it seems.)
4) Cut it into small pieces (about the same size as betta pellets).
5) Feed about a quarter or half the pea to your betta.
The pea has tons of fiber and keeps the betta regular. I advocate feeding just a tiny bit of pea once in a while because people seem to forget that all wild carnivores get a bit of veggies from the stomach contents of their prey. Simulating this in captivity is essential for bettas.