# Smart Low-Cost Control System for Fish Farm Facilities
## 3 Selected Factors for Smart Low-Cost Control Systems for Aquaculture
### Selected Control Factors for RAS  
In RAS systems, technology allows for the control of several parameters of water quality, and sensors can monitor the correct operation of other elements. In addition, monitoring technology can act as a trigger for control technology, activating or deactivating elements to keep the water quality in between desired values. The monitorization of water includes sensors for the following: water temperature, DO, salinity, turbidity, pH, pollution (hydrocarbon, phytoplankton), and current. All these data are needed to activate/deactivate the water control mechanism in the facilities (such as pumping systems, aerators or oxygenators, water heating/cooling, filters, skimmers, disinfection, and salinity correction...). Data can also indicate a general or partial failure of these control mechanisms. The light intensity is another aspect to be monitored since it can indicate a general or partial failure in the illumination system.  
Regarding the biotic factors, fish swimming depth and velocity, fish counting, and estimations of fish size can easily be measured compared with the previous case. The factor of feed falling is less challenging, and cameras can be used. In this case, no fish predators, vectors, or intruders might be in the tanks. Invertebrates or other organisms are considered eradicated by the action of disinfection systems.  
For the control mechanisms, which must include a solid filter, biofilter, aerator, and disinfection, sensor nodes, and sensor actuators are included in each step. The monitoring sensors include a water flow sensor in every mechanism and specific sensors to control the correct operation. The specific sensors are a turbidity sensor for the solid filter, a pH sensor for biofilter, a DO sensor for aeration, and a phytoplankton sensor for disinfection. Moreover, the RAS might include additional steps for heating/cooling the water and for salinity correction; in this case, water temperature sensors and salinity sensors are included.  
Concerning the actuators, for the correct operation of water treatment mechanisms, water pumps to control the water flow and the time remaining in each process are used. Additionally, alarms can be included to alert if an abnormal situation is detected. For the fish tanks, the actuators include three main groups of actuators. First, the water pumping and feeder actuator are to control the water flow and the feed velocity and schedule. The aerator and skimmer are in charge of controlling the water quality at the tank scale. Finally, the actuator for the illumination system controls the light intensity, the photoperiod, and the alarm to alert of an abnormal situation in the tank.  
Figure 10 represents all included factors for RAS facilities. Given the high isolation and control of those systems, most factors are related to the Control Domain and Abiotic Domain.  
Figure 10: Factors considered for Smart Low-Cost Control Systems for aquaculture facilities in RAS. A larger number of factors are included compared with Figure 9. Most of the factors belong to the Control Domain. Only two factors belong to the External Abiotic Domain since the RAS water system is isolated.