I believe that when a fish is hungry it will eat whats in front of it's face. I feed roughly 50# of food a month in my pond, and even tho the fish are there every feeding time, they eat a lot of natural forage in the pond too.
I have a groundwater pond, where water flows in and out with the groundwater.
When the water table was higher and (I believe) not much water was flowing thru the pond, I had a worse algae problem. (nutrients) With the lower water table, and pumping well water into the pond, the algae problem is less, (my SWAG is less nutrients in the water due to water flowing in and out of the pond).
A pond is like an aquarium. Without filtration, the fish are swimming in their own toilet bowl. Filtration comes in the form of phytoplankton, plants, algae and bacteria. The longer you observe your pond, the better you will get at noticing the changes that happen on a daily basis, which will help you adjust how you manage the pond.
I think of fish food like dog food. Higher quality food means less needs to be fed, so less comes out the other end of the fish (or dog) to keep them on an even keel or add weight.
Activity levels change the amount of food needed too. One Springer Spaniel I had would keep her weight the same on 2 cups (16 oz. by measure) of food per day in the "off" season. When we were training for field trials and hunting hard, she needed 2 feedings per day, each feeding was 5 cups. That's on a dog that weighed 30#. Purina Pro Plan was the food year 'round.
