// Closed RAS

Closed recirculating aquaculture system


What's Closed RAS


Land-based aquaculture without water changes

FRD Japan’s closed RAS system uses a unique filtration technology that utilizes bacteria, making it possible to conduct aquaculture while circulating water with minimum exchange.


Technology of Closed RAS

Technology enabling no water changes

Features of Closed RAS

Features of Closed RAS

Conventional recirculating land-based aquaculture systems require water changes of at least around 30% per day, mainly to prevent the accumulation of substances such as nitric acid that cannot be removed.
FRD Japan has developed a “denitrification device” that removes nitric acid with the power of bacteria. This has enabled land-based aquaculture with a completely closed circulation that does not require water changes*. It is a future aquaculture system that allows delicious fish firming at a low cost in any location.
*Only water that is lost through evaporation, etc., is replenished.

Four advantages of Closed RAS

Environmentally friendly

In general, salmon are raised on the sea surface aquaculture. Still, when the scale of farming exceeds the ocean's self-cleaning ability, the sea becomes polluted by feces and food. FRD Japan uses a unique filtration system to circulate artificial seawater, so there is no drainage into the ocean or rivers. This is an earth-friendly sustainable aquaculture method that does not pollute the ocean or rivers.
*ASC certified. ASC certification is a certification of aquaculture products that have been raised with minimal impact on the environment and society.

Aquaculture of "Anywhere Anytime"

FRD Japan's closed RAS system does not require oceans or rivers to be cultured far from the sea, even in the vicinity of consumption areas. It is also unaffected by natural disasters such as typhoons, tsunamis, and the spread of pathogens. We can deliver the freshest fish all year round with minimal transportation costs from the vicinity of consumption areas.

No need for cost of water cooling

In conventional land-based aquaculture, which requires water changes, seawater is drawn from the ocean at the time of water changes, cooled to the appropriate water temperature for the fish, and circulated in the tank. Especially in the summer, the seawater, which can reach 30 degrees Celsius, needs to be cooled down to about 15 degrees Celsius. Thus, the cost of electricity for this process has been a bottleneck for land-based aquaculture. FRD Japan's Closed RAS system eliminates the need for seawater cooling, which significantly reduces electricity costs.

No risk of fish diseases entering from seawater

FRD Japan's Closed RAS system does not use seawater but circulates artificial seawater through a unique filtration system. Since there are no viruses or bacteria from seawater that can cause fish diseases, stable production is possible without antibiotics to deal with them.
// Trout Farming Project

Trout Salmon Farming Business

What's Trout Farming Project



FRD Japan has been building and operating its own trout salmon farming plants. Currently, we are operating a demonstration experiment plant in Kisarazu, Chiba Prefecture. In the future, we aim to spread our Closed RAS system in Japan and other countries around the world.


Future Plans


To popularize a Closed RAS system.

FRD Japan is planning to move from “Phase 1 (demonstration experiment plant)” to “Phase 2 (commercial plant)” to spread the Closed RAS system. We are currently operating a demonstration experiment plant with an annual production capacity of 30 tons as part of Phase 1 and succeeded in stable fish production with minimum exchange.
Phase 2 of the plant, with an annual production capacity of 3,500 tons, is under construction starting in July 2023.

Phase 1:Demonstration experiment plant(30 tons/year)
Phase 2:Commercial plant 3,500 tons /year)

Demonstration experiment plant

Fish species:Salmon trout (large rainbow trout)
Production: 30 tons/year
Saitama Plant (from hatching to 6th month)
Location: Iwatsuki-ku, Saitama City, Saitama Prefecture
Start of operation: December 2017

Kisarazu Plant (from 6th month to shipping)
Location: Kisarazu City, Chiba
Start of operation:July 2018
First shipment:April 2019

Commercial plant

Fish species: Salmon trout (large rainbow trout)
Production volume: 3,500 tons/year

Location: Futtsu City, Chiba
Start of construction: July 2023
// Consultant for participating in Closed-RAS

Support for entering the land-based aquaculture industry

FRD Japan also provides support for companies that are considering entering the land-based aquaculture business. We can assist in selecting fish species, the formulation of aquaculture plans, the design of aquaculture facilities, and other custom-made aquaculture plans. Please feel free to contact us.

Past Cases


Abalone farming with closed RAS system

  • White data center in Bibai city, Hokkaido
  • Sanriku Region Reconstruction Department of Iwate university 
  • Aqua-Agri stationTamagawa University 

Torafugu (Japanese pufferfish) farming with close RAS

  • Shihoro onsen in Hokkaido

Full automatic denitrification device OCN2