Abstract: An apparatus for producing algae circulates algae fluid through flexible reactor tubing that is at least partially translucent to sunlight. The reactor tubing lies flat when not pressurized. Preferably, the reactor tubing is made of clear polyethylene with UV inhibitors, the polyethylene being between 6 and 15 mil thick. The reactor tubing preferably has a substantially circular cross-section with a 6 inch diameter and is preferably 1250 feet long. Gas relief valves allow gases generated during algae production to escape from the reactor tubing. CO2 may be injected into the algae fluid to stimulate photosynthesis. A circulation pump propels the algae fluid through the reactor tubing, keeping the reactor tubing pressurized and stationary without touching the reactor tubing, so that a rigid support structure is not needed. One or more layers of plastic mulch may be disposed above or below the reactor tubing to control temperature and sunlight exposure.