Invasive fish such as koi (or common) carp (Cyprinus carpio) are large fish as adults (typically 1-3 kg) and can exist at high biomass (commonly 1000-2000 kg/ha). Because of their large size, high biomass, and suctorial feeding behaviour that disturbs the lake bed, koi carp have the potential to contribute a significant amount of plant nutrients (nitrogen (N) and phosphorus (P)) to lake waters. To estimate the potential of koi carp to inhibit lake restoration, we estimated the rates of excretion relative to other processes contributing nutrients to lakes.