A RAS system is a aquaculture system in which wastewater (loaded with residues and hazardous chemical components for culture fish) is refurbished by mechanical filtration at tens of micron resolution and by biological filtration to eliminate toxic components.
Also a RAS system recovers the dissolved oxygen level and removes unwanted bacteria or viruses by exposure to ultraviolet radiation.
To be effective, a RAS system must remove as soon as possible these solids and even plant matter, such as micro algae.
An ideal system would eliminate any suspended substance in solid or even semi-solid water within the first half hour of its occurrence.
RAS units control the temperature in culture water, as this is one of the main factors influencing the fish growth rate.
The environmental control system must be able to control the water temperature so that the increase in thermophile performance is optimal without unduly raising the cost of operation.
Water can be heated by efficient heat exchanges, using electrical resistances, boilers and electric or gas boilers, and efficient and environmentally friendly systems by using heat pumps.
Air heating in the growing area can be taken into account, but it is not as effective as other water heating methods.
The use of residual heat from pumps and aerators can also be used to heat the water.
Thermostatic control systems are available for all heating or cooling equipment.
There are also a number of other natural energy sources that can be used to control water temperature, such as solar heating or geothermal water springs.
In RAS systems, the adaptive feeding system that delivers accurate and timely food distribution is extremely important to achieve optimal growth performance and reduce staff operating costs.
The feed frequency (feed time) and the amount of feed delivered depend on the size and species of the fish.
Water temperature is one of the most important environmental parameters that influence the growth and metabolism of fish and, in essence, food consumption.
Mechanical feeders (for example, vibratory band or screw systems) can be used and can be programmed to deliver fixed feed quantities at the default hours and intervals.
These feeding systems, along with mechanical filter cleaning systems, reduce the demand for physical work in the farms.
However, in some situations, manual feeding will be used so that fish can be observed at certain stages of their development.