AbstractA commercial micropulverized 50% crude protein diet for penaeid culture was studied for biochemical oxygen demand and to assess its effect upon water quality in the hatchery and raceway environment. The feed was separated into 13 sizes ranging from 250 μm to 2 mm in diameter. The first order reaction rate constant (k) increased with decreasing particle size. The micropulverized feed was highly biologically reactive and the rate constant (k) varied from 0.1 to 0.24 day‐1, depending on the particle size. The ultimate BOD was 660 mg/g. The goal of this research was to predict the impact of this feed in relation to varying particle size upon the oxygen and ammonia dynamics of the water. This information will enable shrimp hatchery managers to more effectively assess the water quality impact and water replacement schemes when using artificial micropulverized fee