Let's suppose that you were raising any animal crop be it chickens, mice, rats, cats, rabbits sheep, pigs or foxes and yes even fish in a pen or pond.
Feeding the animal crop even more increases productivity as more biovolume /biomass. What will happen if you allow them to continually breed in the pen or POND, then regularly increase the food amount to them due to more animals and then did not regularly remove some??? Just because you cannot see all of them does not mean they are not present. Eventual overpopulation, crowding, lower body weight, poor health, sickness and deaths. Use your common sense and manage the numbers of fish that each year keep reproducing in your pond. Harvest, harvest, harvest even if it is small fish. In the water it is difficult to actually see how many fish are present and how much they are being crowded.
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