An open pond bioreactor is used to grow a photosynthetic algae in Nevada as fish food. During the day it is operated as a continuous culture with an objective of maximizing biomass output. The strategy is to supply sufficient CO2 and nitrate to allow cells to grow as fast as the light source will support. However at a cell concentration greater than 1 g/l, the specific growth rate begins to decrease from μ0=0.69 hr-1 as described by the following equation because of decreased light penetration. To supply the algae with the carbon source sodium carbonate is added as the feed and the culture is operated at a steady state. The CO2 concentration in the pond is maintained at 0.03 g/l, a sufficient level to support maximum growth rate. The conversion efficiency for C02 to glucose by photosynthesis is 100% (i.e. all C02 taken up by cells is converted to glucose.) However, among the glucose assimilated only half by mass is converted to Determine the optimal dilution rate to maximize biomass output and the sodium carbonate. (Na2 C03) feeding rate (g/l hr). MW: Na 23