The Big Fish RAS System

Introduction to Recirculating Aquaculture System


A land-based Recirculating Aquaculture System (RAS), is a low impact aquaculture process that has the potential to meet the world’s growing need for protein with minimal effect on the environment. Over the past 30 years, the development of Recirculating Aquaculture Systems (RAS) has made it possible to culture fish under completely controlled conditions, anywhere in the world.


The basis of the technology is the recirculation of water inside a land-based fish farming system, whereby the same water is recycled in a closed circuit, thus minimizing the amount of new water that needs to be added to the system.

The team at Assentoft Aqua has been involved in this development since the very beginning of the recirculation aquaculture industry, thus learning from both successes and failures from existing plants, including salmon plants.

The Big Fish System

Following are the many key benefits of a closed (or RAS) fish farming system:
• Optimal use of feed
• The ability to regulate and control the internal habitat to match the cultured species;
• The ability to reduce invasive fish diseases from the surroundings;
• Easy control of temperature, salinity, oxygen and pH to meet the requirement of both the cultured species as well as the Different growth stages, i.e. whether to induce spawning, wean fish larvae or simply grow fish to market or re-stocking sizes;
• Fast growth of fish during the whole year due to a controlled environment.

The Big Fish System

Assentoft Aqua has developed a unique system for breeding fish in the range from 500 g. up to 5kg Tanks can be configured to fit customer requirements with side-boxes, degassers, central outlets etc.

Features of Large Scale Big Fish RAS System

Assentoft Aqua is second to none in the following :
• Production Capacity  – Up to 10,000 metric ton
• Energy efficiency – per KW needed for 1kg production
• Size Range – From 2 to 6 kg
• State-of-the-art RAS water treatment modules – with well-proven technologies and track records
• Fast installation with steel-tanks as basic components.
• Built-in Firewall for Bio-secure Production.

The Assentoft’s Advantage

Assentoft Aqua is second to none in the following :
• Having the lowest possible footprint – saves space, pipes, buildings etc
• Having a fast installation time by using steel tanks as our basic component
• Having the best available water treatment within the industry
• Inventing new creative solutions for the industry
• One of the lowest investment per produced ton of fish
• Deep knowledge about Pelagic fish production in land-based RAS-systems

Prefabricated RAS treatment unit

An Assentoft Aqua RAS treatment unit can be shipped in containers and erected by a trained crew in a very short time. It can treat up to 5000 m3/h of water and 2500 kg of feed per day. It can be connected in many ways with few big tanks or a higher number of smaller tanks.

Assentoft Aqua’s moving bed bio-reactors are unique in nitrification and for breaking down organic biomass (BOD), and its continuous aeration avoids any formation of H2 S. The submerged up-flow in the fixed bed bio-reactors is very good at entrapping small particles. When the water is treated in an MBBR, the organic load is low, and the particles are inert. The fixed bed reactor can be managed safely without risk of H2 S formation

Grow out tanks

Assentoft aqua can provide bolted Glass enamelled steel tanks or stainless steel tanks or Stainless-steel tanks in any size. They can be shipped in containers to any location and can be erected fast on concrete foundation. The surfaces are smooth and easily cleaned.