Abstract:
Nitrogen is an important element in aquatic environments. Utilization of nitrogen contained in the feed as a source of energy and simultaneously toxic to aquatic systems, especially in catfish ponds. The nitrogen concentration in the form ammonia is toxic to catfish if it higher than lethal dose 0,6 mg N/l, so the nitrogen concentration in the form of ammonia has to be kept at low value, below 0.6 mg N/l. The interactions between various nitrogen are complex and difficult to analysis. However, it can be described by a mathematical model. So the dynamic modeling and simulation aimed to predicting the nitrogen dynamics and study the effect of variations in eviromental management is a % protein in feed, feed rate, and water exchange rate on nitrogen dynamics. In this research variation % protein feed used were 20%,30% and 40%. Variations feed rate based on fish weight were 2,9%, 3,9% and 4,9% and water exchange rate used were 5%, 10% and 15%. The data conditions of catfish pond and initial value of nitrogen concentration were obtained from literature. Nitrogen dynamics model which formed a system of ordinary differential equation 1 was solved by Runge-Kutta order 4 method. Models was implemented using Matlab. The result accumation N-NH3 of All variations of pond management below of N-NH3 toxicity limit for catfish is < 0.6 mg N/l. However, the concentration of N-NH3 should be kept from 0,02 to 0,08 mg N / l. So the recomended management treatment is giving 20% protein, 2,9% feed rate and 15% rate of water exchange.
