Concrete Pond

    In Okinawa, Japan, the first attempts at creating a commercial production method took over 5 years to develop, with a trial and error during those 5 years. This resulted in a successful way to grow green caviar seaweeds on land using concrete ponds – small ponds of seawater that have tightly controlled environments. These ponds are much more convenient for the workforce which is mainly comprised of older people. The water is not deep and green caviar seaweeds can be easily retrieved without any diving involved. This method is akin to growing vegetables hydroponically – they can control the light levels, the salinity of water, the temperature as well as nutrients which the green caviar seaweeds need. This allows them to control the production from start to finish, giving them the ability to schedule harvests year-round as you can see from the table below.

 A group of Japanese local farmers use large warehouses for this purpose, with glass ceilings that allow light to pass through. The green caviar seaweeds are attached to nets and allowed to soak in a pre-prepared concrete pool with a depth of about 30-40 cm. There are blinders that prevent too much light from entering on sunny days. Air is pumped into the pool in order to artificially simulate a current which allows the green caviar seaweeds to receive appropriate nutrients. The water should contain no less than 0.05 ppm of ammonia, a pH level of 8-9, a salinity level of no less than 28-30 ppt and a temperature of 25-32 degrees Celsius (optimal temperatures being 27 degrees).

   For this reason, green caviar seaweeds are unable to grow in colder areas – Europe, South Korea, and many other countries have an average temperature of fewer than 20 degrees Celsius. Japanese grow their  green caviar seaweed by making them resort to using fertilizers with nitrogen and phosphorus every 2-3 days, for a period of around 30-45 days before harvest. This method is not fully organic, as it relies on a constant stream of fertilizers to create their product.

green caviar seaweeds grown on nets/grids
Buildings used for green caviar seaweeds cultivation
Risk of contaminated substance??


-a constant production rate year-round, and can be produced ahead of time.

-It does not use nutrients from the soil, so there is less need for the addition of nutrients.

-Meets the demands of consumers more consistently.


-It has a high production cost and uses a lot of labor.

-Requires a large number of workers to care for every grid, clean, cultivate and harvest daily.

-The minerals in the water may not be enough for the green caviar seaweeds to fully grow, compared to raising them naturally in a pond.