Large‐scale artificial upwelling was tested as a method to enhance the environmental conditions for the growth of non‐toxic algae in a Norwegian fjord (61°0′N, 6°22′E). The experiment was designed to evaluate if nutrient‐rich seawater, brought up from below the mixed zone of a stratified fjord to the euphotic zone by air bubbling, would stimulate the growth of non‐toxic relative to toxic algae. Pumping 44 m3 min−1 of air at 1 atm through a pipe diffuser submerged at 40 m depth formed a buoyancy flux that lifted 60 m3 s−1 of deep water to the upper 17 m over a period of 21 days. The supply of silicate, inorganic nitrogen and phosphate to the upper 10 m in the fjord increased, and a significant increase in the biomass of non‐toxic algae was observed. The upwelling gave an increased growth of the non‐toxic dinoflagellates Ceratium furca and C. tripos. After termination of the experiment, the phytoplankton biomass decreased significantly, whereas a distinct increase occurred in the relative biomass of the potentially toxic Dinophysis spp. The result is considered promising when it comes to creating controlled geographical areas with non‐toxic food for mussel production.