highest stocking densities
by effective enrichment
with technical oxygen

Increasing demands of fish quality, higher stocking densities, declining water supply and the use of high quality, expensive feed necessitate more effective oxygen transfer methods than surface aerators alone. With surface aeration, it is only possible to achieve a maximum of 100 % saturation, and then with the expense of high energy costs. This is because oxygen is only present in air at a low concentration (about 20 %).

This is the reason why the peak demand of oxygen in many operations cannot be covered any more with surface aerators. Due to this, a situation of lack of oxygen (at least temporarily) occurs.

During periods of low oxygen, feed is poorly digested. The fish subsist, resulting in little or no growth, and poor health. Oxygen is a very important factor in fish farming. With abundant dissolved oxygen, fish growth is maintained, food conversion rate is optimised and less faecal waste is generated. In addition, fish health improves, and they are less susceptible to disease. These benefits result in cost savings.

A ‘fish stock formula’ can be found by referring to the technical literature. From this it is possible to calculate the fish stock in kilograms per litre of intake water. The most important factor when calculating stock capacity is available oxygen and oxygen consumption per kg of feed. A simple example will readily illustrate the importance of adequate oxygen levels. Example: a pond at 250 m altitude, stocked with 10 cm long rainbow trout, water temperature 10 °C and a daily feeding rate of 1.5 % of the bodyweight. With a dissolved oxygen saturation of 10 mg/l (= 90 % saturated) this formula calculates a production of 1.3 kg trout per litre intake water. If the dissolved oxygen concentration can be increased to 11.1 mg/l (= 100 % saturated) the production will increase to 1.7 kg trout per litre intake water. This corres ponds to an increase of 30 %.

This example illustrates the profound effect that oxygen has on the stock of a pond, and shows very clearly the potential offered by the use of oxygen with effective enrichment systems. Clearly, the decision to use pure oxygen in fish-farms is cost effective because the environment for the fish can be 100 % oxygen-saturated all year round. LINN Gerätebau has developed specialised oxygen-enrichment systems for this purpose. They are used directly in the pond, usually floating like an aerator. LINN systems offer high oxygen transfer rates with high dissolution efficiency.

Comprehensive information and technical data on the different LINN systems appear on the following pages.


  • floating compact enrichment system
  • pioneering technology
  • safe operation / maintenance free
  • motor located above the water surface
  • low energy costs - very effective
  • clogging free
  • available in two size 0.37 and 0.55 kW

Additional Information:

Datasheet LOXY

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  • oxygen enrichment in a self-contained system
  • almost silent
  • lightweight and compact
  • higly efficient - special LINN mixing device!
  • tested and reliable
  • available in 4 sizes from 0.10 to 0.75 kW

Additional Information:

Datasheet OXYPLUS

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OXYPLUS gravity

  • oxygen enrichment system for use with an existing pressure head 
  • works without additional motor/energy 
  • specific, effective LINN mixing device
  • available in various sizes: floating or stationary

Additional Information:

Datasheet OXYPLUS Gravity

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  • open input enrichment system
  • ideal for use in reciruclation complexes
  • ensures a good water circulation and oxygen enrichment
  • available in six sizes - water flow 2 - 60 l/s
  • oxygen enrichment 3 - 40 l/min

Additional Information:

Datasheet OXYJET

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