John Rutz wrote:
I visited a Large pond a few years ago at a resort that had several 36"
+ carp that did quite well on popcorn, that was all they were being fed

That may be all they "were being fed," but I'm sure they were finding
plenty of other things to eat in that pond: algae, plants, larvae,
insects, small pond "critters," caviar, etc.
--
Kathy B
Zone 6