Aquafarm Equipment AS

Closed Cage


The closed cage is built from GRP elements and reinforced with steel in areas that endures the most stress. The cage consists of several elements bolted together with use of a special technology.

The design also includes a pump system, which, through a strainer unit, extracts large volumes of water from a depth of 25 m or more.

The pumps have a high efficiency and reliability securing very low operating cost, and installation above sea level gives easy access for service and maintenance. A specially designed hatch system is installed in the side walls. The hatches are patented and give an exceptional hydraulic flow inside the cage. A separate (optional) system for inserting oxygen into the water flow is also located on the barge.

As the concept of the cage is to collect the waste from the fish and feed it may be located inside fjords and close to the shoreline. Waste from the fish and other pollution in the cage is collected in the sloped bottom cone. A flexible pipeline connects to the low point and leads up to the mud separator.


The closed cage from Aquafarm Equipment AS uses the lightweight material GRP with local reinforcements of high tensile steel. GRP has been proven to be an excellent material for fish farming and is used in many tanks for smolt. We have taken this line of thinking a large step further and made a floating cage.

The design consists of several elements fixed together with specially designed joints. This makes both transport and installation easy and affordable.

The size, thickness and geometry of the elements are shaped to give an optimal strength to weight ratio.

Neptun has now been tested for well over a year and proven to meet all the criteria’s we defined in the design.

Technical Data:

  • Inside diameter: ø40 mmodeller
  • Circumference: 126 m
  • Cage Depth: 22 m
  • Gross Volume: 21.000 m3
  • Significant Wave Height: Hs = 1,0 m
  • Max Wave Height: HMax = 1,8 m
  • Design Wind : v = 30 m/s (Severe Storm)
  • Current: 0,75 m/s
  • Lifetime: 25 years
  • Certified design and construction according to NS9415:2009

Cost Factors

The investment cost for a Neptun Cage is somewhat higher than that of a conventional system. However the benefits of the closed cage will soon come to light and reveal many advantages.

In addition to direct sale we can offer both rental and leasing agreements. Please contact us for further details.ID-100272287

  • The design life for the Neptun Cage is 25 years – strong and durable materials are selected to keep the maintenance cost as low as possible.
  • High quality and very efficient pumps ensures low power consumption.
  • Expenses due to escapes and change of nets are no longer a factor.
  • Cost of delousing is reduced to a minimum – if any at all.
  • The mortality rates are well below the rates in conventional cages. In the prototype the rates was below 1% up to 1 kg.
  • As the waste is collected the Neptun Cage can be located close to shore saving transport cost for both personnel and equipment.
  • The growth factor has proven to be excellent in the Neptun Cage – saving a lot on feed.

All in all the Neptun closed cage will prove to be a better investment after a short period of time.

The Challenges

Jumping SalmonOne of the major issues in the fish farming industry is the impact it has on the environment. The use of medicine and chemicals to handle sickness and lice in addition to the waste from the farm are issues that are discussed in may forums.

Fish escaping may possibly endanger the gene pool of the wild salmon population. It is also assumed that the resurgence of lice will increase the spread of disease.

The waste from the fish and other substances used to run a fish farm often ends up in the sea or on the seabed. Several tons of waste will accumulate. There are different views on what the impact on the local environment is.

The Solution

To help solve these challenges was our main impetus for the development of the Neptun Closed Cage. Trough full scale testing during 2013/2014 we have proven to meet many of these challenges.

As the Neptun Cage is made from solid components, escapes are no issue.

In the closed cage, the water is pumped up from a depth not normally inhabited by lice and other organisms.

As a result of this the use of chemicals and/or medicine may be drastically reduced in the Neptun Cage.

Our Cage includes a system for separating and extracting waste from the fish. Full scale testing has proven to collect as much as 60-80%. A second generation separator is currently being developed.

Moving the cage due to local environmental overload might no longer be an issue.

There are several parameters that influence the fish health. The Neptun Cage has proven to meet many of these through various concepts.

PetitSaumonThe pump capacity and the hydraulic design ensure fresh water throughout the whole cage. At full power the total cage volume is replaced more than 32 times a day. The current induced by the pumps gives the fish a continuous flow of water and simulate the sea current. In addition oxygen is distributed inside the water flow, – the O2-saturation is monitored and may be regulated to the optimum for the fish.

As the water in the cage is extracted from >25 m, the temperature is more stable through the seasons and optimal for fish growth. This depth is also believed to be below the normal area for lice and other organisms in the water, hence, a large reduction of lice, contamination and infection is the result.

All these factors put together has shown to give increased growth, low mortality and a more healthy fish.

The full scale test gives these results:

up to 1 kg => 0,4 %

Feeding Factor:
up to 1 kg => 0,87

UNI Miljø (UNI Environment) carried out research for Aquafarm Equipment AS in regards to fish health within closed cage systems. Their report had three focus areas:

  • Lice, Algae and Jellyfish
  • Water Flow, Oxygen and Temperature
  • Water Circulation and Current

Four researchers spent time at the closed cage and concluded positively in their report on all areas.

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