International Journal of Aquaculture, 2025, Vol.15, No.1, 11-20 http://www.aquapublisher.com/index.php/ija 13 The inclusion of açaí was achieved by adding distilled water at 55 °C to promote the gelatinization and agglomeration of the starch. After this process, the mixture was homogenized in a horizontal mixer until a semi-solid consistency was reached. The pelleting process was then carried out using a die with a 2.5 mm opening. The feed pellets were dried in an oven at 50 °C for 6 hours, broken, and sifted to separate the granules sized between 2 and 2.5 mm and stored at ~20 °C until use. The proximal composition of the formulated diets (Table 1) was determined following the methods established by AOAC (2016). Crude protein (N × 6.25) was determined by the Kjeldahl method. The crude lipid content was evaluated using a Soxhlet extractor with solvent extraction (petroleum ether). Crude fiber was analyzed through acid and alkaline digestion of the samples, as described by Silva and Queiroz (2002). Table 1 Ingredients of the experimental diets and analysis of the centesimal composition before and after the inclusion of açaí Ingredients (%) Diets DC0.0% DA0.5% DA1.0% DA1.5% DA2.0% Fishmeal 30.00 30.00 30.00 30.00 30.00 Soybean meal 25.00 25.00 25.00 25.00 25.00 Wheat flour 15.00 15.00 15.00 15.00 15.00 Soybean hulls 15.00 15.00 15.00 15.00 15.00 Fishoil ≤5.00 ≤5.00 ≤5.00 ≤5.00 ≤5.00 Cornbran 15.00 15.00 15.00 15.00 15.00 Premix1 ≤4.00 ≤4.00 ≤4.00 ≤4.00 ≤4.00 Crude fiber 4.50 4.50 4.50 4.50 4.50 Moisture 12.00 12.00 12.00 12.00 12.00 Proximal composition before the inclusion of açaí (g/kg) Moisture 100.0~120.0 100.0~120.0 100.0~120.0 100.0~120.0 100.0~120.0 Crude protein 360.00 360.00 360.00 360.00 360.00 Ether extract 50.0~80.0 50.0~80.0 50.0~80.0 50.0~80.0 50.0~80.0 Crude fiber 20.0~40.0 20.0~40.0 20.0~40.0 20.0~40.0 20.0~40.0 Mineral matter 70.0~100.0 70.0~100.0 70.0~100.0 70.0~100.0 70.0~100.0 Total carbohydrates 350.0~400.0 350.0~400.0 350.0~400.0 350.0~400.0 350.0~400.0 Proximal composition after the inclusion of açaí (g/kg) Moisture 55.20 57.97 62.23 68.93 59.57 Crude protein 359.60 360.30 358.60 348.20 356.75 Ether extract 80.65 84.50 82.55 86.50 88.75 Crude fiber 15.70 16.65 26.50 14.50 24.50 Mineral matter 97.33 97.03 97.27 95.40 98.20 Total carbohydrates 392.00 385.00 370.00 391.00 372.00 Sodium 2.90 2.95 2.90 2.90 2.90 Note: 1 Vitamin A (10 000~15 000 IU/kg). Vitamin C (500~1 000 mg/kg). Vitamin D (2 000~3 000 IU/kg). Vitamin E (100~200 mg/kg). Vitamin K (5~10 mg/kg). B1-Thiamine (20~30 mg/kg). B2-Riboflavin (30~50 mg/kg). B3-Niacin (100~200 mg/kg). B5-Pantothenic acid (50~100 mg/kg). B6-Pyridoxine (20~30 mg/kg). B7-Biotin (1~3 mg/kg). B9-Folic acid (10~20 mg/kg). B12-Cobalamin (0.02~0.05 mg/kg). Choline (1 000~2 000 mg/kg) 2.3 Experimental design A total of 240 juvenile koi carp were distributed in 20 tanks with 80 L of water at stocking density of 12 fish per tank and 4 replicates each treatment. The animals were acclimated for 10 days and were fed with the feed recommended by the producer during this period. The tanks, containing the fish, were connected to a recirculating aquaculture system (RAS) consisting of a clarifier, mechanical and biological filters, and a UV reactor, with a
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