Samples of lettuce, fish, and fecal solids were collected weekly, dried to a constant weight at 66°C, ground in a Wiley mill, and stored in scintillation vials for proximate analysis. Fish samples were redried at 105°C prior to proximate analysis. Three water samples were collected twice weekly from each system. Two samples were immediately frozen at −28°C for later NO3-N and mineral analysis. The third sample was analyzed for total ammonia nitrogen (TAN), NO2–N, and alkalinity using test kits (Hach, Loveland, CO). Water temperature and pH were recorded each time water was collected for the determination of unionized ammonia levels, and water level was recorded so nutrient concentrations could later be corrected for differences in system volume at the time of sampling. Water lost to evaporation and transpiration was replaced daily with distilled water.