Aeration may be provided with a roots blower, rotary blower or an air compressor. A blower provides large volume of low pressure air while an air compressor provides small volume of high pressure air. An air blower runs continuously while a compressor which is equipped with the pressure tank runs whenever the pressure is low. The compressor automatically switches on when pressure drops below a pre-determined level. In a hatchery, low pressure air available at large volume is more desirable than high pressure air at small volume. Moreover, the hatchery tanks are seldom more than two meters deep. Rotary air blowers are not designed for oil free operation and have a tendency to blow oil particles into the air line producing oil slicks on the surface of the water. Air filters at the inlet and outlet pipes are therefore needed. When the capacity of an air blower is less than 10 HP, ordinary air filters for automobile may be used at the inlet pipe, however, for blowers with high horsepower ratings, synthetic foam can be used. Adjustable pressure tank with resin glass beads or Bagasse as filter materials are used for the outlet pipes. The roots blower is more appropriate for hatchery purposes because it seldom breaks down, less complicated to use and does not produce oil slicks (Kungvankij et al., 1986).

Since continuous aeration is essential to the survival of larvae in high density, any prolonged power interruption would seriously affect the culture organisms in the tank. Thus, it is essential to install an automatic switch which starts a standby generator whenever there is a power failure. A battery operated warning device to signal the crisis and the required operation of the standby generator can also be used (Kungvankij et al., 1986).