Aquaculture, also known as aqua farming, is the discipline of commercially farming aquatic organisms such as fish, crustaceans, mollusks, and aquatic plants. Aquaculture involves cultivating freshwater and saltwater populations under controlled conditions—in contrast to commercial fishing, which is the harvesting of wild marine fish. 

SOLVOX® OxyStream, developed by Linde Gas (www.linde-gas.com), has been proven to improve the living conditions of fish inside the tank. It allows for a significant increase in fish production volume; optimizes fish meat quality; and considerably improves operations from an environmental standpoint. Since the launch of the technology last year, interest is burgeoning in this unique new lowpressure oxygenation system that is poised to transform the world of aquaculture.

The uniqueness of the technology is based on its ability to perform three critical functions in one system—dissolving oxygen in the water, producing the correct hydrodynamics, and stripping out potentially harmful inert gases like nitrogen—all via a very low energy requirement. The system is easily installed, including as a retrofit to existing fish tanks, and is virtually maintenance-free.

The technology has been developed by Linde in response to a progressive trend to move aquaculture production from sea cages to land-based sites for the full duration of a marine fish’s lifecycle. This change has presented the industry with the challenge of oxygenating large fish tanks that can accommodate fish stock from infancy to maturity.

“The limitation with a conventional onland tank is the amount of oxygen available to the fish. Water can only provide a certain amount of oxygen, which is quickly respired. There was therefore a need to provide an additional source of oxygen,” explained Stefan Dullstein, Head of Industrial Segment Aquaculture & Water Treatment at Linde.

The limitation with a conventional onland tank is the amount of oxygen available to the fish. Water can only provide a certain amount of oxygen, which is quickly respired.

Ground-breaking patented SOLVOX® OxyStream is a combined oxygenation and flow system that not only dissolves the optimal amount of oxygen in the inlet water flow, but also distributes it evenly at an adjustable flow pattern through the tank, ensuring fish stock benefit from the physical exercise involved in swimming against the current. The flow regime can be fully tailored according to fish size, stock density, and fish species, such as salmon or cod. The system comprises a standalone unit and is installed individually in each tank, so water flow and oxygen dosing can be individually controlled for each tank.

The micro-bubbles created by SOLVOX OxyStream create the additional benefit of helping to reduce the concentration of dissolved inert gases such as nitrogen or argon. In particular, oversaturation of nitrogen, even in relatively small quantities, can endanger the wellbeing of fish stock, slowing growth and increasing the possibility of disease, and ultimately, even mortality. With the installation of SOLVOX OxyStream, external degassing units to prevent inert gas build-up will, in many cases, become obsolete.

Depending on the application, pumping pressures as low as 0.05 to 0.2 bar are normally sufficient to oxygenate the incoming water, strip nitrogen, and create optimal tank hydrodynamics. This low operating pressure makes the system very energy efficient. OxyStream also requires very low maintenance, because it is not associated with any ancillary equipment to manage water pressure.

“Linde has always played a pioneering role in gas technology within the food production and processing market, and we’re delighted to be able to introduce such an effective and environmentally sustainable solution to combat the challenges of dissolving a sufficient amount of oxygen in very large tanks and distributing it evenly via an adjustable flow regime,” added Dullstein.

The aquaculture industry has responded to the introduction of this system with interest and Linde currently has about 20 pilot units at customer sites, with many more proposed. The company has fielded enquiries from North America, the UK, Norway, France, and even from Saudi Arabia.

“In fact, interest levels are so high that we have to accelerate our activities to meet customer demand,” Dullstein commented. “This is a customized solution; each customer application is unique and needs our professional input.”

Dullstein says Linde’s latest customers are thrilled with the quality of the fish product being achieved. To showcase its technology, Linde is constructing a brand new test center in Norway where customers will be able to see SOLVOX OxyStream in action as it operates in windowed tanks. Training and equipment testing will also be carried out using the new center as a base.

Dullstein envisages a very bright future for SOLVOX OxyStream. He believes the vigorous interest being shown by aquaculture farmers is just the tip of the iceberg.