An algae production reactor system comprising a reactor vessel which is disclosed. The system comprises (a) one or more liquid inlets and one or more liquid outlets; (b) one or more gas inlets at the bottom, the gas inlets being connected with a source of carbon dioxide, and one or more gas outlets at the top of the vessel; and (c) vertically interspaced and joined pairs of double glass plates which are at least partially submerged in the reactor liquid, the double glass plates having a layer of light-scattering particles in between and having a flat side being exposed to a light source, wherein part of the spaces between the double glass plates is arranged above the gas inlets for vertically circulating reactor liquid.