Once removed from the male's mouth, the half-developed larvae are incubated in glass aquarium tanks, measuring 90 x 45 x 45 cm. Water temperature is kept around 27 - 29°C using a thermostat heater and dissolved oxygen is maintained at about 5 ppm (mg/l) through continuous gentle aeration of the water. We generally add about 2 ppm of Acriflavine solution to the water to prevent infection of any injuries suffered by the larvae during handling. Using this in vitro hatching technique, the survival rate to free swimming stage is generally about 90 - 100%.
During the first few weeks when the larvae still have a large yolk sac, they tend to remain at the bottom of the tank most of the time. The fry start to swim upward periodically when the yolk sac becomes smaller. On the 8th week the yolk sac is nearly fully absorbed and the fry start to swim horizontally. At this stage the first live food should be given to the fry. The yolk sac is fully absorbed and the fry become free- swimming at about 8.5cm in length.
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