Effect of formulated and supplementary feeds on water quality parameters in concrete ponds stocked with Oreochromis shiranus fresh water fish

A study on the effect of formulated and supplementary feeds on water quality parameters of fresh water fish (Oreochromis shiranus) culture was conducted at Lilongwe University of Agriculture and Natural Resources Fish Farm for three months. The experiment had four treatments (commercial feed A (31% CP) + chicken manure (T1), maize bran (9.82% CP) + chicken manure (T2), only chicken manure (20% CP) (T3) and commercial feed B (22.64% CP) + chicken manure (T4)) replicated three times. Water quality parameters such as dissolved oxygen, temperature, conductivity and pH were measured twice a day on a eight hour time step using multi-probe water checker. Phosphorus was determined once every three weeks in the laboratory using ascorbic acid method. Total ammonia nitrogen was also determined to calculate unionized ammonia. Statistical analysis was performed using SPSS version 20. The pH ranged from 7.1 – 9.0 in the morning (6.00 am) and 8.2 - 9.4 in the afternoon (2.00 pm). Temperature, dissolved oxygen, conductivity, unionized ammonia and phosphorus ranged from 25.13±0.29 0C to 25.24±0.33°0C, 6.59±0.29 mg/L to 6.31±0.34 mg/L, 310 ±0.01μSe/cm to 320 ±0.01μSe/cm , 0.01 ±0.01mg/L to 0.02±0.01 mg/L and 0.38±0.12 mg/L to 0.57±0.08mg/L, respectively among the treatments. The results indicated that all water quality parameters were within recommended range for O. shiranus. The study found that the formulated and supplementary feeds did not affect dissolved oxygen, temperature, conductivity, unionized ammonia, and pH. However, phosphorus levels were a little bit higher, due to aging of ponds and additional phosphorus released from the chicken manure. The study suggested that using formulated and supplementary feeds in the pond within recommended range during culture of O. shiranus is ideal for having water quality parameters within acceptable range.