Dissolved oxygen and temperature were monitored twice daily; and ammonia, nitrite and nitrate and pH were monitored once a week. Dissolved oxygen and water temperature were monitored with a YSI 55 oxygen meter. The pH was measured using a digital pH meter Alfakit AT350 using the electrometric method. The concentrations of ammonia (NH4+/NH3) − N, nitrite (NO2) − N, nitrate (NO3) − N, were analyzed using the colorimetric method according to procedure described by Strickland and Parsons (1972).