A membrane photobioreactor was designed, implemented and used to grow the cyanobacterium Arthrospira platensis PCC 8005 in batch mode. Growth was followed directly by monitoring optical density and indirectly by measuring pressure increase due to the oxygen produced and separated from the liquid phase by diffusion through a hydrophobic membrane, and pH increase due to carbon consumption. When the pressure attained an upper limit, valves opened automatically, and the oxygen in the gas chamber was flushed out with nitrogen. As expected, two growth phases were observed, a short exponential phase followed by a linear phase, indicating limitation by light transfer. Growth rate during the second phase was measured easily and accurately, and consistency of optical density, pressure and pH data values was checked using a model of the system. Pressure measurement was found best suited to monitoring and measuring growth rate in space in terms of accuracy, precision and reliability.