There is a need for sustainable, efficient, and productive agricultural practices. Goals to improve these practices include reducing water consumption, increasing vegetable culture density, and maximizing livestock feed conversion efficiency. Aquaponics offers the potential to address these goals with intensive production of fish protein and vegetable biomass within one recirculating system. This study explores the relationship between pH and the biomass yield of lettuce (Lactuca sativa cv. Ridgeline Romaine) grown in an aquaponics system with Nile tilapia (Oreochromis niloticus). Optimal pH for aquaponics production has not been clearly established. Four treatments will be studied: a hydroponic control at pH 6.0, and three aquaponics units at pH 6.0, 7.0, and 8.0. Water within each 50L... fish/nutrient tank is mixed and aerated with airlifts. Water flows by gravity from the bottom of each tank into an adjacent column providing additional aeration, and filtration. Water from each column is pumped to the top of three stacked trays, and then cascades down via gravity to a second and third tray before returning to each respective tank. Each tray has 8 lettuce plants growing in nutrient film technique (NFT) culture under LED light. Ten cycles of lettuce harvest will provide fresh and dry weights of shoot and root tissue biomass. This data shall be analyzed for significant difference between treatments using repeated measures ANOVA. If evidence of an optimal pH for aquaponics systems is determined, operation of aquaponics systems will be further improved.