Current demand for water is increasing daily. While the problem of fisheries problems and the amount of fish. The problem of environmental degradation of natural resources in natural water resources are dwindling number every day. To compensate for the output of aquatic animals from natural water sources. It has encouraged farmers to turn to aquaculture more. Choosing the type of fish to feed is one of the factors that farmers use to select and invest. Fish that are resistant to changing environment and economic fish such as Anabas testudineus the digestibility of residues from bio-gas waste. Bio-gas waste to substitute rice bran for growth and yield and to study cost reduction. The study pH optimum functional activities of digestive enzymes and found that levels of two types of pH. Affect the activity of the enzyme amylase, trypsin and extracted from the gastrointestinal (digestive system) of Anabas testudineus. The activity of the enzyme amylase has the highest average at pH 10 and the activity of the enzyme trypsin activity with the highest average pH 6. Therefore, the information obtained from this study can be used. To study the optimal temperature for both enzymes. Therefore, the information obtained from this study can be used. In the cost study, treatment of control 0% (T1), which contained no residue of biogas, had the highest production cost and decreased respectively.