Our Developed Technology

Recirculating aquaculture systems are highly technical installations, where the success of operations is dependent on the right choices of technology. In effect, this means that both design and operations involve high-tech elements where cross-disciplinary engineering is needed.

As the water is recirculated, much emphasis is put on the water treatment systems and its chemical, biological and physical properties. Further, the handling of the fish, the growth rates during various stages, the logistics of the fish handling affects all aspects of the design implementation.

Our mapped-out facility has more than 98% recirculated water. Our process design has minimal effect on the surrounding biotope. Nitrogen, phosphorus and particulate wastes will be recycled and not contribute to eutrophication. The fish species, Arctic Char, has an optimal growth at high fish density, and is therefore attractive for large scale cultivation. The design will farm the fish from fry to growout product. Arctic Char is a cold-water fish and water temperature will vary between 5 and 18 °C depending on life stage. The design will perform cooling and heat exchange with minimal loss. By controlling the whole process, from fry to harvest, we optimize water utilization, we avoid excessive transports, and we build a unique understanding of aquaculture design.


Water quality is fundamental to fish health. In landbased systems the water is purified and reused. The fish density in the water tank is dependent on aeration, byproduct concentration and fish natural preference. The biochemistry of fish affects the production of by-products and thus the load on the system's water treatment system. The water turnover rate is tuned after the fish growth and related metabolism. High water quality at a high percentage of recirculation and low pump cost is achieved when equipment is selected and tuned to the waste load. We optimize new and existing systems with our advanced models and cross-disciplinary considerations.

Typically an indoor aquaculture has a 95% water reuse every hour. CDEng has designed a system with up to 98% recirculation. In the water fish respirate, feed and execrete byproducts. With every recirculation particulates are removed, carbon dioxide is stripped, water enriched with oxygen and disinfected from virus and bacteria by oxidation methods. When the fish decompose the feed, ammonium nitrogen is formed which is converted by the water purification system to harmless ammonium nitrate. Depending on the size of the facility a different selection of mechanical, chemical and biological treatment is appropriate.

Every organism’s life and environment is dynamic. Water emissions will vary with feeding events, light cycle, fish physical activity and other factors. In our chemical models, we take into account these variations and advise on how to fine-tune your system. In dimensioning a new system or upgrading an exisiting one, we find the best match of modern water technology and fish health.


By-product flows from your process may consist of bleed-off water, sludge, and filleting wastes. Up to 5% of the water is discharged every hour in order to counteract ammonium nitrate build-up. Nitrogen and phosphorus emissions can cause eutrophication to lakes and waters. With modern water technology and knowledge within fish farming we can minimize your water use and protect the surrounding biotope.

The recirculated flow is filtered and solid matter separated from the aquaculture. These particles of different sizes form a malodorous sludge. After thickening to a lower water content, the sludge may be suitable for biogas production.

Upon harvest the residues from filleting are excellent rawmaterial for animal feed. With consideration to the size of your aquaculture and your fish species of choice we can optimize your by-product flows.

Fish Feed

Fish feed is one of the largest costs in fish farming. Optimal feed utilization can be achived with good management. Success requires knowledge on fish growth rates and skilled interpretation of fish response. Typically feed consumption is 0.8-1.5 times the weight gain of the fish. The fish species and physiology determines the maximum use of the feed. The nutrition of the feed and energy and protein content must be adapted to the fish species. The feed type and pellet size are adapted to the fish species and developmental stage.

The fish size is measured every day and the expected growth decides the amount of feed supplied. Fish farmed in good water quality will live more stress-free. Aggression in some individuals can cause uneven growth and poor feed utilization. CDEng's water chemistry models ensure a design that is customized for your fishs’ health and optimal feed use.