The carrying capacity would increase.
Increasing the amount of a limiting nutrient (such as nitrogen or phosphorus) in a pond can enhance the growth of primary producers, such as algae and aquatic plants. When these producers thrive, they can support a larger population of consumers, such as herbivorous fish and other aquatic organisms. This means that the pond can sustain more life overall, thus increasing its carrying capacity.
However, it is important to consider that excessive nutrient addition can lead to problems such as algal blooms, which can deplete oxygen levels and create dead zones, ultimately harming aquatic ecosystems. But in general, moderate increases in limiting nutrients typically lead to an increase in the carrying capacity of a pond.