The LCS I kept in my aquarium fed heavily on the algae that grew in it. So much so I started to encourage its growth to give them something extra to eat. They also readily fed on frozen daphnia, bloodworms, glassworms and mosquito larvae. However, I could never get them to take commercial food regularly. They would filter the sand on the bottom of the tank, sucking in amounts and filter it out through their gill openings and I am assuming removing what food items they found in it.
Buying large amounts of frozen bloodworms could get a bit pricey... I think they would do fine in a pond that has some age to it, as the wild food Bill mentioned should be abundant.
