Freshwater RAS Technology

Freshwater RAS Technology & Protein Skimming technology has been introduced to marine aquaculture hatcheries and RAS farms since the 90’s. What is the innovation of MAT-KULING in freshwater aquaculture and especially in salmon farming?

Freshwater ras technology

Freshwater Aquaculture

Protein skimming is often used to withdraw organic compounds such as various floating compounds, different viscosity liquids, proteins and amino acids, resulting in reduced ammonia and nitrite levels, allowing higher oxygen concentrations within the system, providing significant increase in biological filtration capacity. Achieving higher biological capacity in the same volume holding tanks, results in better farming practices.

Freshwater farmers, especially salmonids farmers, requested MAT-KULING to develop a Freshwater Foam Fractionator device that would operate in fresh and brackish water conditions to be installed in pre-smolt stages tanks. A bypass filtration technology that could enhance water quality by 20% or more would change the way farms work today. We got this challenge very seriously and invested in manufacturing trial equipment and started test them in farm conditions to overcome the known problem of low surface tension of the fresh water. The obstacle to overcome was to produce and sustain sufficient amount of fine and thick constant air bubbles within the skimming trench in order to generate sufficient skimming. At that time, most of the available fresh water skimmers in the market failed to keep stable production of thick protein foam. After 3 years of trials we are finally proud to present the newly developed Fresh Water Protein Skimmer (FW-PS).


NIVA (Norwegian Institute for Water Research) officials, performed an independent, field trial on MAT-KULING freshwater protein skimmer performance in a salmon farm in Norway and reported more than 70% particles removal.

Particles removal during time diagram in freshwater protein skimmers
Particles Removal During Time in Freshwater Protein Skimmers

Freshwater Protein Skimmers

Freshwater protein skimmers in action
Freshwater Protein Skimmers in Action

The principle is rather simple but the engineering behind achieving optimum results needed many trials in various bioloads and water viscosities. Basically, we optimized the polarity of the organic compounds in fresh water environment, achieving significant levels of protein reduction from the water column.

The Freshwater Protein Skimmers simply put, operates by producing thick sludge of fine air/ozone bubbles of which surface area attracts protein-amino acid molecules and other organic and inorganic compounds through which the skimming process is achieved by expelling out this bubble-organic sludge through a foam discharge chimney, located at the top of the device. The key to achieve optimum performance was, to ensure operator friendly stable production of fine air and ozone bubbles that could be sustained, until, the discharging point at the top of the PS chimney. The freshwater protein skimmers operate using purpose designed and built venturis in conjunction with booster pumps to achieve high pressure conditions within the PS body.

MAT’s newest Fresh Water Foam Fractionator is designated to serve Fresh and Brackish Water RAS Facilities, providing an efficient system addition to enhance floatable and dissolved solids control. As it is well established in salt water conditions, the device, is capable to control the fine particulate matter mechanically removing it from water and additionally, through the fractionation process, the equipment minimizes bacteria and microorganisms concentrations in close circuit systems as it improves the Oxygen and Ozone infusion into the processed water. We strongly recommend the use of ozone infusion within the Protein Skimmer body.

It has been observed the freshwater foam fractionator’s performance is even better on higher organic loaded systems. Our site tests showed a decrease in total suspended solids, ammonia, nitrite values and achieved increase of dissolved oxygen and ORP values.

Freshwater Protein Skimmer Models
How does a Large Protein Skimmer / Foam Fractionator work?

MAT-KULING kick started on-site tests the world’s largest salmonids farms. The testing environment is the RAS system of a fully stabilized RAS smolt production. Take advantage of this new technology and contact MAT-KULING for more details.