Nutrient cycling is key to ecosystem functioning and maintaining balance across trophic levels. Consumers are central to this process, selectively taking up, storing, and releasing nutrients in ways that shape primary productivity and biogeochemical processes. Freshwater fish, for example, continuously exchange water through their gills, releasing limiting nutrients like phosphorus that primary producers can uptake. Despite the importance of consumer-driven nutrient recycling (CNR), we lack a mechanistic understanding of how ontogeny and demographic structure influence nutrient fluxes, especially in species undergoing rapid evolutionary change. Consumer traits like nutrient consumption, assimilation, allocation, excretion, and egestion change significantly as they grow, so linking these shifts to demographic structure is critical for predicting population-level contributions to nutrient recycling. This project investigates how nutrient storage and recycling shift across ontogenetic stages in Poecilia reticulata, a globally invasive fish species with well-documented variation in growth rates. We reared guppies adapted to high- and low-predation environments on different diets and across ontogenetic stages to quantify how dietary phosphorus is assimilated into the body and allocated to bone for storage and to RNA for growth. We also measured excretion rates to determine how much phosphorus is returned to the environment. Excretion analysis is underway, and the body nutrient, bone, and RNA analyses will begin in February 2026. Studying invasive species like guppies is especially important in a changing world, as their rapid life histories and adaptability allow them to alter nutrient dynamics and adversely affect native biodiversity and ecosystem resilience.