- Temperature is the most important variable affecting the growth of larvae and early juveniles.
- The optimal temperature for growth appears to be 30°C; however, temperatures in the range of 26-33°C are known to yield acceptable growth performance.
- At temperatures below this range, growth rates decrease but survival is still good. However, 28°C is the optimal temperature for both yolk sac absorption and maximum growth rate.
- High temperatures can encourage the growth of harmful bacteria and fungi, however.
Tolerance of low dissolved oxygen (DO) concentrations
Catfish can withstand very low dissolved oxygen levels, but well–oxygenated water is recommended. This is easily achieved by means of aeration or good flow rates.
- A salinity range of 0-2.5 parts per thousand (ppt) appears to be optimal for young catfish.
- Larval growth is acceptable in up to 5 ppt salinity, and survival is good up to 7.5 ppt.
- Optimal survival is achieved when larvae are reared in continual darkness, and larval growth decreases with longer periods of light.
- The free-swimming embryos (hatchlings) shy away from light and are said to be photophobic. They form aggregations on the bottom of the incubation tank.
- Taking advantage of their photophobic behaviour, it is possible to concentrate them in a dark corner of the tank and to remove both deformed and weak hatchlings using a siphon.