Well, what I like about ponds is that quite a lot of natural food comes along for the fish to eat - algae building up on the walls, mosquitos and other insects falling into the pond.
It also depends on the size of the fish, and if its koi or goldfish. My hubby feeds his koi once a day with big koi pellets, and he just tosses a handful of them into the pond.
My goldfish get fed twice a day with soaked food, bloodworms, and they have the algae to eat. I watch them eat for a few minutes, and if there is still food left after that, I give them a little less next time. You kind of develop an eye for it, and with watching you'll also figure out which ones are the food horders that gobble up more food than the others.