Development of a Solar Based Automatic Water Heating and Temperature-controlled Recirculating Aquaculture System

Recirculating aquaculture systems have proven very successful in resolving problems relating to water shortages for fish production and increased yield as the stocking density is important. These systems however consumed much energy in running pumps and heating of water since temperatures play a critical role in fish growth. The main objective of this study is to contribute in putting in place a stable automatic temperature-controlled recirculating aquaculture system capable of using water and energy in an efficient manner. The aim is to develop a system that can use 1000 L of water and grow fish to maturity. The system consisted of a 1000 L capacity tank, a mechanical filter, a bio rock filter, a de-nitrification tank with water hyacinth, an aeration system, a 12 V solar pump, a solar water heating system, and computerized automatic controls using the Arduino microprocessor. Everything was powered by 100 Watts solar module connected through a charge controller to a 200 AH Battery. One hundred catfish fingerlings were raised in a period of 8 months. Water from the fish tank move by gravity to the mechanical filter before being pumped to the bio rock filter. From the bio rock filter, the water moves to the de-nitrification tank. From the de-nitrification tank the automatic control system either sends it back to the fish tank or directs it through the solar water heating if tank temperatures are below 25°C. In order to assess the performance of the system, physical and chemical water parameters were measured. These included the total dissolved solids (TDS), pH, electrical conductivity (EC) temperature, dissolve oxygen, ammonia, nitrite, and nitrates. Results showed that the average daily weight gain of catfish fingerlings was 0.39±0.28 g and that the physical and chemical water quality parameters were at optimum levels for fish growth. It was concluded that such a system can enable farmers to grow fish to maturity in a region with limited water and energy resources.