Fry cultivation can be carried out using various structures such as nursery equipment, cement pools, cages, or ponds. This section will focus on the process of raising fry in ponds. Typically, the ponds used for fry rearing range from 3/15 to 5/15 hectares in size, with a water depth of approximately 0.6 meters. One month before stocking the fry, the pond should be thoroughly cleaned and disinfected. Once the disinfectant has fully dissipated, the pond is filled with water up to about 30 centimeters. After that, fertilizers are added to promote the growth of zooplankton, which serves as a natural food source for the fry. Once the fry are introduced into the pond, the water level is gradually raised by 5 to 10 centimeters every few days until it reaches 60 centimeters. Within 20 to 30 days, the fry will grow to about 0.8 to 1 cm in length, at which point they can be moved to the summer feeding stage.
For the summer feeding phase, the pond size is more flexible and not strictly limited. Before introducing the fry, the pond is treated with lime to eliminate harmful organisms, and the water is fertilized to support aquatic life. The stocking density usually ranges between 900,000 and 1.2 million fry per hectare. Initially, the water depth is kept at around 0.5 meters, and it is gradually increased as the fish grow, reaching a maximum depth of 1.2 meters. Starting from the second day after stocking, the fry are fed twice daily. In the first week, soy milk is used as a primary feed, and later, commercial compound feeds are introduced. After approximately 40 days, the fry will have grown to 7 to 10 cm in length, making them ready for further development or transfer to larger systems.
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