Looking for thoughts on feeding and general care tips.

When I received my group, they were hungry with sunken bellies. I placed them in an established tank filled with java moss to the point you can't see a thing. Sponge filter and plenty of wood in the tank as well. I had removed all previous occupants some days prior. I decided not to feed an allow them to adjust to the new tank. In the morning all of them had very full bellies. I've had this group of fish for some time now and feed small portions of live blackworms, as well as various frozen and dried foods. Since the tank is so heavily planted, I honestly don't know what the fish are eating. I can tell they always appear well colored, full and happy so something must be right but I'm not sure what foods I should be focusing on.

What have others had success with as far as feeds and tank arrangement for this fish? What did my new occupants eat overnight to give them such full bellies?

Each other.

I haven't kept them before, but I would expect them to be like other small killies, like bluefins. I feed mine frozen mysis, tubifex, and bloodworms. It sounds like there are a bunch of tiny living inverts in your plants, so you could try a daphnia culture. Or just add some pond/river water once a week or something.

Maybe pygmies were feeding on microfoods off of your plants. You know the slime on the plants? Maybe they love it? That what happen to my guppies when I put them in planted tank and next day the guppies were full and the plants looks slime-free.