RAS Fish Farming: What Should You Know About It?

RAS Fish Farming Concrete Pond

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Over the years, aquaculture (fish farming under controlled conditions) has resulted in an ample supply of seafood consumed globally.

Recirculating Aquaculture System (RAS fish farming) is a new practice in a closed system.

It is a new and distinct way to farm fish.

Fish farming has to do with the commercial production of fish, done in an enclosure with a controlled environment (RAS) or in a body of water.

Aquaculture as a farming system.

What is RAS in Fish Farming?

Fish farming was traditionally done either outdoors or in an open pond. Due to the decrease in fish population due to water pollution, there has been a decline in fish production.

Recirculating Aquaculture System or RAS seeks to promote an environment where fish farming takes place in contaminant-free water in an indoor tank system.

RAS is a new and unique way to farm fish instead of the traditional method of growing fish outdoors and in open ponds. This system occurs mainly where water exchange is limited.

It involves recirculation and filtration of water. The system goes through biological and mechanical purification methods. The filtration system is necessary to remove suspended particles and other toxic wastes.

RAS has become advanced, geared toward land-based production. This indoor fish farming method adopts high-density cultivation of different fish species using only a little land and water area. The indoor fish farming method is a better alternative to low-density fish cultivation in open ponds.

Is RAS Fish Farming Profitable?

With RAS, yield, cost, and flexibility are what push profitability.

Because RAS allows for maximum optimization and high-density cultivation of tilapia fish, African catfish, and other types of fish species, there are more yields of fish which means more profits.

Also, RAS fish farming uses recycled water; the water is purified, filtered, and recycled back for use. There is thus judicial use of water supply.

The cost associated with feed and disease control lessens because there is the monitoring of feed within 24 hours, and the RAS can potentially eliminate the release of parasites.

Cost of fish feeds in Nigeria.

Flexibility to the location of farming and closeness to the market enhances the profitability of RAS. It is possible to manipulate production and harvest made in the most profitable time of the year.

Moreso, the equipment used for this system is durable.

How To Start a RAS Fish Farming

Are you thinking of starting RAS fish farming? Here are things you should know.

  • Sales: Making use of the assumed sales price is not ideal. Sometimes prices fluctuate based on seasons or increases or decreases in production.

It would be best to establish sales price and volume from time to time to give credibility.

According to James Steeby, you should ask questions like ‘What product value is missing in my target audience? Someone considering going to RAS fish farming would consider species, sizes, taste, packaging, volume, and value-added.

  • Tank Size: There are different available sizes and shapes of tanks. However, a circle or oval shape is preferable to a rectangular outline; this is because a circle or oval shape facilitates easy water circulation and easy cleaning.

The capacity of the tank depends on the type of fish, water requirement, and stock density.

The size of the tank ranges from 500 to 500k gallons depending on the amenities.

Alongside optimal waste removal, we have outlets attached to the tanks.

Check out tank sizes used in fish farming.

  • The flow of pump and water:

The constant water flow prioritized itself in the RAS fish farming system, and speed alteration is possible whenever required.

The pump is placed outside and works on high pressure. Water is pumped to an elevated level and begins to flow. This is made possible through gravitation.

  • Cutting grown grasses: The fish tank needs proper aeration; thus,  grown grasses around the fish tank should be cleared.
  • Getting a balanced PH level: The PH level should sustain the fish to survive well.

Typically a PH between 6-9.5 is advisable. Buffers like Sodium Bicarbonate and Calcium Bicarbonate can aid the maintenance of the PH level.

  • Feeding the fish: This involves how to feed the fish.

Feeding the fish is done according to the weight and growth of the fish. Usually, the fish uses  3-5% food daily of their body weight.

The feed should contain high protein with all essential minerals. Take note also of specific fish feeds.

Overfeeding can cause contamination of water. Feeding the fish should thus be done on a regulated schedule simultaneously daily to maximize growth.

The feed is stored in a cool, dry place free from insects and rodents and ordered at a limited supply enough to feed the fish and avoid waste.

  • Financing:

You will need funds to start up RAS, either privately, through grants, or through loans. If you want to bring in investors, bring in skilled people with technical know-how.

At the Federal and state level, there is only limited assistance rendered to fish farmers.

Aquaculture establishments are championed mainly through private financing.

The federal-state marketing improvement program (FSMIP) is a program carried out by the Agricultural marketing service (AMS) of the USDA to offer assistance to aquaculture.

  • Legal restrictions: Before venturing into RAS fish farming, you would want to know what is legally acceptable in this fish farming system.

The aquaculture system is subject to federal, state, or local regulations.

These regulations have restrictions on pollution and discharge of wastewater effluents, fish transportation (Intra and inter), and species of fish to be reared and sold.

Another thing to know before starting RAS fish farming includes the equipment to be used, which would be discussed below.

RAS Fishing Equipment

To know how RAS work, we look at the equipment used. For example, aeration devices help to recycle water after eliminating pollutants.

The equipment used for RAS is listed below:

  • Bio-filters: The biofilter is a piece of essential equipment in RAS, used to detoxify harmful waste(ammonia and nitrites) and uneaten fish feeds.

Biofilters capture hazardous chemicals, and wastewater is also processed using bio-filters.

Type of biofilters.

  • Pumps: Because a large quantity of water is needed to sustain the fish’s environment, Pumps are adopted.

Pumps fill small ponds and lakes used for fish farming with fresh water from a more comprehensive freshwater source.

They are used to recirculate water back into the fish tank.

The general type of pump used in the RAS fish farming system is the centrifugal pump. The pump is usually placed outside and works at high pressure.

Gravitation aids the movement of water.

  • Aeration devices: As earlier mentioned, aeration devices help to recycle water after removing impurities; this is important for the fish’s respiration.

Through aeration devices, fish is reared in large quantities using only a tiny space.

  • Generators: In fish farming, Ammonia Nitrogen wastes breed bacteria in water. However, the Recirculating Aquaculture System makes it possible to maintain good water quality.

Ozone, a volatile gas produced and used at the site, is an excellent oxidant free of secondary pollution. Ozone improves water quality and effectively kills viruses produced by ammonia nitrogen.

How ozone decomposes oxygen.

Design of the ozone generator.

How the ozone becomes toxic.

In general, yield increases as fish growth boosts. John Davidson and co-workers studied at the freshwater institute to determine if ozone generated a beneficial water quality.

The study showed that rainbow trout growth was, to an extent, higher in lower exchange RAS operated with ozone than in the non-Ozonized system. In conclusion, the study proved that ozone created a more excellent optimal water quality environment.

  •  Grading equipment: In harvesting fish, grading equipment is necessary to grade the fish into different sizes.

Other components in RAS include; Water tanks, Fish tanks, UV sterilizers, Sludge collectors, an insulated shed, settling tanks for sludge, a water testing kit, a store cum office for feed and accessories, etc.

We now look at the type of fish suitable for rearing in fish farming.

What Fish is Suitable for the Recirculating Aquaculture System?

RAS uses warmed and recycled water; thus, cold-water species of fish are not suitable for RAS.

However, a variety of fish species which include:

  • Barramundi/Asian sea bass
  • Tilapia
  • Pangasius
  • Rainbow trout
  • Cobia
  • Silver
  • Catfish
  • Pearl spots are convenient for farming in recirculating systems.

Advantages of RAS

  • It is the best type of aqua system that can be used in the city
  • It helps manage the water system

Disadvantages of RAS.

Although the prospect of RAS is good, there are downsides to this system.

  • The recirculating system operates on an uninterrupted power supply. Backup power is always required.
  • The feed must have high protein quality and be easily digestible.
  • Only technically skilled staff working in a medium technology environment are suitable for RAS.
  • The recirculating system uses good water sources, preferably boreholes.
  • Human errors can lead to a loss of stock density and cash.
  • Everything about aquaculture is super risky.


One main advantage of RAS fish farming is its ability to reuse water and maintain an enabling environment for the fish.

The RAS promotes the proper functioning and management of fish farming. The growing demand for healthy fish led to the rise in the aquaculture system.

The open system of farming which includes other farm animals has proven less productive than the closed system. This will likely be the case for fish rearing and cultivation.

It should be noted that no system is 100% closed. The inability of a system to be entirely closed is due to loss by evaporation.

The outlook of the recirculating systems projects is favorable for intensive fish farming in the future.

If you think RAS farming might be quite expensive for you to start, then you can start a fish farm the traditional way by reading the article I wrote about how to start a fish farm.


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