Water quality variables were monitored during 3.5 years of research on pig-fish, duck-fish and chicken-fish systems. Early morning dissolved oxygen levels were often below 0.5 mg/1. Total ammonia levels were highest in chicken-fish systems with maximum levels exceeding 6 mg1. Water quality sampling designs which measure the fluctuations in water quality variables are discussed. Species selection, control of manure loads, addition of new water, and aeration are presented as means to manage water quality in livestock-fish systems.