A closed tubular horizontal photobioreactor with the ability to produce industrially delicate microalgal species was assessed and validated. A co-current gas–liquid flow was chosen for mass transfer along 1,200 m piping which delimited a culture volume of 4,700 L. Mixing was obtained by means of hydrodynamic events accompanying this type of flow, including waves. The constant cross section of the piping allowed the circulation of spherical bodies to wipe the inner wall and avoid the establishment of a biofilm. Two similar reactors were constructed in December 2009 and December 2010, and operated to supply the dermo-beauty care industry with active biomass of three delicate species of microalgae, including the chlorophyte Neochloris oleoabundans and the rhodophyte Porphyridium cruentum. Daily observed production of dry biomass varied between 0.2 and 1.7 kg, depending on the species, the sun exposure and the period of the year. The ability of this production system to reduce the cost of producing algal biomass through scaling-up is discussed.