Aquaponic systems are integrated systems that combine fish farming and different types of plants. It involves a dynamic interaction between fish plants and bacteria. Fish and plants are dependent the equilibrium of dissolved nutrients and water quality. Only by striking a balance between dissolved nutrients and water quality we can achieve a large production of plants and healthy fish. Thus, control of water quality in an aquaponic system is essential in order to obtain performance in raising fish and plants. The experiment was conducted in the laboratory of Fisheries and Aquaculture of the Faculty of Animal Science of the University of Agronomic Sciences and Veterinary Medicine of Bucharest within a period of 30 days. The system used for the experiment was designed and developed in the laboratory mentioned above. The plant used for water treatment in the system was basil (Ocimum basilicum). Fish species grown in the system was culture carp (Cyprinus carpio). Indicators measured to assess water quality in the system were: temperature, pH, dissolved oxygen, total ammonia, nitrites, nitrates and phosphates. The values determined pH 7.4-7.6, dissolved oxygen 8-10 mg / l, NH₄ 0.05-05 mg/ l, NO₂ 0.1-3.2 mg / l, NO₃ 0-80 mg / l, 0.02-0.3 mg, PO₄ 0.02-0.3 mg/l were not too high. In conclusion it was demonstrated that water quality in the aquaponic system studied is propitious to the growth and welfare of fish the registered values are not to be harmful.