I feed mine, mostly because I have two kids that love to do that. If I didn't feed them, I'd make sure I had a lot fewer fish. I feed worms to the Bluegill, who won't touch the Rangen.
I often find goldfish or koi mutt babies in "fish free" pots, the upper pond, and the swamp pond. Those fish never get fed, yet they're big; so I have to agree that it doesn't matter that much, depending on the fish load. The fish I find in those places are a surprise, and I'm usually amazed at how big they are cuz I don't feed them for months, and only discover them late in the season and they're huge.
Most fish food isn't really "food" anyway: it's wheat, corn, soy, and a bunch of other garbage grains and industrial cr@p that fish weren't designed to eat in the first place. Fish in the wild know exactly what to eat to maintain health: Bugs, plants, smaller fish, worms, crustaceans ... not corn
If the small pond can't provide that, a shovel (and a couple of kids) comes in handy.
Of course if you're like me, you get nightmares of kids digging up your yard. Holes everywhere, shovels missing, plants gone... happens every day.
. My turtle friend pays .10 for every cricket the kids can catch.