Specific diversification is one of the Greek Research & Development approaches for minimization of production problems related with exponential development of marine aquaculture, because it allows the farmers to open new markets. Among all the alternatives of diversification, those related to high growth, medium priced fish (Thunnus tynnus, Coryphaena hippurus, Polyprion americanum, Seriola dumerilli) and to lower growth, better priced fish (Pagrus pagrus, Dentex dentex, Puntazzo puntazzo, Spondyliosoma cantharus, Diplodus sargus, Epinephelus sp.) are more discussed. Some of these species are actually grown, but the majority of the biological basis for their reliable culture is yet unknown.