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The PaRAS partial recirculation concept uses slightly more water than recirculation aquaculture systems. However, partial recirculation is a significantly simpler and often a more affordable option for environmentally friendly fish farming than recirculation aquaculture systems. The first three years have produced excellent fish farming results. Fish grow more quickly than in recirculation aquaculture systems, and the expensive purging phase is not necessarily required before selling the fish.


  • Improved fish growth
  • Improved fish quality
  • Lower investment and operating costs
  • All-in-all-out production strategy
  • Can be divided into compartments

In the PaRAS recirculation concept, partial recirculation tanks are connected to a bioreactor. As aeration and flow systems and solids removal systems are tank-specific, tank units can be isolated from centralised biofiltration without any impact on feeding or production. When new fish are brought to a farm, for example, a tank can run on partial recirculation separate from the rest of the farm, until the health of the new fish group has been ensured. A tank can also be isolated and switched to partial recirculation when fish are depurated for sale.


  • Tank-specific aeration
  • Tank-specific solids removal
  • Easier fish logistics, causing less stress for fish
  • Hybrid farm option

In the PaRAS purging concept, fish can also be fed during the purging phase without losing any of the grown biomass. PaRAS tank units can also be used as purging tanks without any modifications. In a rectangular tank, various fish groups can be separated using partitions, and they can be guided towards harvesting by moving gates. Even a smaller fish group can be harvested without causing any stress for other fish in the same tank (and without fasting).


  • Can be used as a purging tank without any modifications
  • Fish can be harvested more easily without causing any stress for other fish in the same tank
  • More effective purging – no biomass losses

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Jouni Peltomaa
+358 50 518 3581

Tapio Kiuru
+358 40 750 1883