The microalgae Neochloris wimmeri, Scenedesmus vacuolatus, Scotiellopsis oocystiformis, Chlorella zofingiensis and Protosiphon botryoides were grown under secondary carotenoid inductive conditions. The results indicate that nitrogen deficiency and high light intensity are potential inducers of astaxanthin formation in the five microalgae studied. All these microalgae accumulate significant quantities of secondary carotenoids, mainly as astaxanthin esters and canthaxanthin. They also showed high resistance to environmental conditions. All these qualities make these microalgae good candidates for successful culture in open ponds.