THE RAINBOW TROUT is one finicky fish. Native to the cold mountain streams of North America, Europe and north Asia, it demands water temperatures between 10 and 14 degrees Celsius, high dissolved oxygen levels and fast-flowing, clean, gravel-bedded streams to sustain its near-constant movement.
In India, only the Himalayan region (Jammu and Kashmir, Himachal Pradesh, Uttarakhand, Sikkim and Arunachal Pradesh) can meet these demands. This is thanks to year-round glacier melt, steep gradients that keep water oxygenated and minimal stagnation, even in summer. No other landscape offers this combination. In fact, efforts by Scottish planters to grow trout in Kerala’s Munnar, between the 1890s and 1920s, had failed. Now there is only limited trout presence in Munnar.
In that context, what Aditya Ritvik Narra has built in Hyderabad is remarkable. Through his SmartGreen Aquaculture, he has created India’s first inland trout farm, in one of south India’s hottest cities, using recirculating aquaculture system (RAS) technology to simulate the necessary conditions. The farm was inaugurated in January by Union Fisheries Minister Rajiv Ranjan Singh, who has, in Aditya’s words, become “a brand ambassador for the trout farm”.
RAS is, at its core, closed-loop fish farming. It grows fish indoors. Temperature, air and water quality are controlled and continuously monitored. RAS is widely used for high-value fish like trout and salmon, and shrimp, especially when water is limited or climate conditions are not ideal.
In RAS, water from the fish tanks passes through mechanical filters to remove solid waste, and then biological filters where beneficial bacteria break down ammonia (which can accumulate as it is expelled by fish). Oxygen is replenished and the treated water is returned to the tanks—all in a continuous, automated loop. Nothing is discharged. Even the solid waste collected from the tanks is converted into oil that can be mixed back into fish feed.
SmartGreen’s chief scientist G. Sampath Kumar said that if the conditions outside are compatible (during cooler months), the system lets air in, reducing energy use. At the heart of it all is a SCADA (supervisory control and data acquisition) dashboard that tracks eight parameters, such as power and oxygen, in real time. A deviation triggers an automatic alert. In case of a power interruption, there are two backup generators.
The farm’s fish tanks are circular, 2m to 4m in diameter and 6ft to 10ft high, built from food-grade steel, plastic and metals. Since trout never truly stop moving (they slow down to sleep) motors spin the water in the tanks at 1,800rpm.
Aditya’s fascination with fisheries began during engineering. A stint at a firm in Visakhapatnam gave him exposure to seafood processing and export. Eventually, he focused on RAS technology and joined all available courses in India and abroad. He settled on trout—the second-most researched fish after salmon, and known for rich nutritional content and anti-ageing effect—after considering different fish. A reason was Hyderabad’s thriving film industry giving rise to a number of people looking for food with anti-ageing properties.
“I have visited the US, Denmark, Norway, Iran and Turkey to study both trout and the technology,” said Aditya. “I also visited the trout farms in north India and studied the technology from Indian institutions.”
He started R&D in 2019 on a six-acre plot on Hyderabad’s suburbs. But, Covid-19 led to the project being stalled for nearly two years. When the lockdown ended, the entire effort had to start from scratch. “RAS is not generic technology, but customised,” said Aditya. “For every unit, parameters change and calibration needs to be careful.”
The 31-year-old says that one of his motivations behind starting the farm was proving that RAS technology could succeed in Indian conditions. Why? “Because the current aquaculture practices are not sustainable, and RAS is the future,” he said.
Beyond the novelty, the farm demonstrates something significant to national interests. RAS dramatically outperforms traditional aquaculture. Where conventional methods require 1.5kg to 1.8kg of feed to produce 1kg of fish, RAS needs only 0.9kg to 1.1kg. Also, while it takes three years to grow 1kg of fish in natural conditions, RAS can do the same in just one year.
Indeed, if climate-controlled aquaculture is replicated elsewhere, that would open up fisheries production to geographies previously considered unsuitable, thereby helping increase exports from India. Thus the interest from the Union government. Aditya has been made a director of the National Fisheries Development Board in recognition of his work.
Aditya admits that RAS is a money and electricity guzzler. “We have so far invested about Rs50 crore in the project,” he said. But, he adds that money can be made once the RAS unit is fixed. SmartGreen currently produces 360 tonnes annually against a plant capacity of 1,200 tonnes. The farm is selling about 100kg of fish every day; the target is to sell 500kg per day. Whole fish sells at Rs1,500 per kg and fillets Rs3,000—steep considering Hyderabad’s popular fish varieties, which range from Rs200 to Rs800 a kg—and is supported by a growing base of loyal customers and strong export interest from markets in the US, the Middle East, Japan and Singapore.
It is planning to offer consultancy services, franchise and franchise-owned and company operated model. “The pie is so large,” said Aditya. “We need a lot more players to come into trout farming.”