Gilthead sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) are the marine fish species most reared in Portugal. Both are cultured in a semi-intensive mode, typical of the Southern Algarve. Their production starts with juveniles which are reared in hatcheries and fed with pellets, reaching values of 10 tons per hectare and per year. In the earth ponds we have identified an important population of macrobenthic invertebrates - polychaetes (82.1 per cent), bivalves, amphipods, chironomids, phoronids. In these aquaculture systems, the reared fish eat pelleted food, leaving the natural food sources available for other fish species which could then be reared as a co-culture. The sole (Solea senegalensis) seems to be the best choice for (i) bioecological reasons: it is a locally abundant species and is being produced in hatcheries with growth and survival rates compatible to those of other commercial species and (ii) economical reasons: it is highly demanded in the market and it would diversify the offer of the aquaculture products. The principal obstacle in the aquaculture of S. senegalensis is the non-existence of commercial diets; however, its main natural food source consists of polychaetes which is the most abundant taxonomic group in the earth ponds exploited for gilthead sea bream and sea bass. Moreover, the fact that there is no competition for the water column between these species, makes S. senegalensis a candidate for co-culture with S. aurata and/or D. labrax. This work: (i) describes the most common fishculture plants used, the methodologies to be applied and the goals of productivity to be achieved and (ii) considers the implementation of the sole culture in the earth ponds, based on its bio-ecology and the scientific data already available.