Recirculating aquaculture system

This article answers the question on, “what is Recirculating Aquaculture System?”. The Merits and Demerits of RAS, it water treatment process, and the types of Recirculating aquaculture system.

Read on to discover and get familiar with these information for your fish Farming experience.

What is Recirculating Aquaculture System

Recirculating Aquaculture System is also known as RAS. It is a system which involves the
Purification and continuous reuse of water. This method of water recirculation is usually done in home aquaria and fish production farms. It is used where water supply is limited. Water is treated in a closed system using biofiltration and other filtration method to provide clean and healthy habitat for aquatic lives.

Recirculating Aquaculture system is done to ensure a toxic free habit for fish, provide ammonia free water. It maintain good aeration, clean water and reduce the need for the demand of fresh water. Solid waste and non degradable product are removed during water purification and filtration.

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Merits of Recirculating aquaculture system

Here are some of the major advantages of using the RAS method.

  1. Reduction in wastewater effluent volume: RAS, helps to reduce the size or volume of waste water effluent since water is treated and reused. Only solid and non degradable waste products are disposed while the water is reintroduced back to the tank after treatment.
  2. Reduced water requirements: It is economical using RAS when compared to other aquaculture system. This system makes it possible for you minimize water wastage especially in areas or situations where water is hard to access.
  3. Increases Biosecurity and reduces disease outbreak: Recirculating aquaculture system helps to treat water and remove harmful toxins, and chemicals from the water. It helps maintain water pH level, stabilize aeration and reduce or eliminate diseases.
  4. Due to high stocking density of fish, land need and it use is reduced. Other available land space can be used for other purposes. This helps to reduce cost of land acquisition.
    Recirculating aquaculture system offers the opportunity to be in full control of your fishes. You have the opportunity to monitor environmental impacts and increase productivity.
  5. This aquaculture system offers the opportunity to be independent of large clean water source. Proximity to steady water source will not be a factor in RAS, because of water reuse. You will only need to add little water quantity from time to time after treatment.
  6. It helps to optimize your fish feeding strategy.
  7. This system makes it easy to sort and harvest your fishes.

Demerits of Recirculating aquaculture system

It is a normal phenomenon for RAS to have disadvantages. Although, it’s demerits are less when compared to the good side of it. Below are some of the constrains RA system has.

  1. Technical know-how: Running a RAS requires at least a medium skill tech staff to operate. Getting a good skilled staff to manage this system may not be easy to come by.
    If the technical staff leave the aquaria for any reason, the fishes may suffer large mortality.
  2. Cost of RAS: It requires a good sum of capital to set a recirculating aquaculture system. The running, electricity and maintenance cost is relatively high.
  3. Greenhouse emissions is usually higher in a recirculating aquaculture system compared to non RAS.

Recirculating Aquaculture system Water Treatment process

Recirculating aquaculture system is done in order to treat and maintain fish water quality. To achieve this, there are processes required which must be carefully followed.
The water treatment process discussed below has to be completed properly to have a healthy water for your fishes. This is so that you will have a bountiful harvest of quality fishes and high growth rate.

1. Biofiltration

Biofiltration is the first step of water treatment process for the recirculating aquaculture system. This treatment process is done to convert excreted ammonia from fish to nitrate which is less toxic to fish. Biological filtration provide substrate for bacteria community which allow the generation of thick biofilm within the filter.
Nitrifying bacteria are chemoautotrophs that convert ammonia into nitrite then nitrate. Biofilters are used to convert this ammonia to nitrate by allowing bacteria use up the ammonia for energy.

2. Solid waste Removal

After treating the liquid waste, solid waste treatment follows. This is carried out successfully by using either drumfilter, mechanical filters and/or sedimentation filters.
Solid waste removal increases aeration, slows down the growth of diseases and bacteria.

3. Oxygenation

Oxygen is very essential for the growth and production of fish. After the above two water treatment processes, oxygenation and/or aeration is the next step.
Fishes and bacteria in the biofilters require oxygen to complete their metabolic process. To achieve this, an oxygenator or aerator will be required to pump air or agitate the water slowly.

4. pH control

Some of the treatment processes like the biological filtration alters the pH level of the water. After these processes, it is important to check and ensure that the pH of the water is kept at normal.
You can achieve this by addition of lime or sodium hydroxide. It can also be done by degassing with an oxygenator or an aerator.

5. Temperature control

Ensure that your water is at the right temperature to avoid suffocating the fishes. Warm water fish are okay at 24°c while cold water fish prefer temperature lower than 15°c. Use a thermometer to determine the temperature of the water and environment.
To maintain the right temperature, chillers, heat exchanger and heat pump can be used.

6. Biosecurity

Viruses and bacteria should be eliminated correctly to avoid diseases outbreak. It is important to clean and sterilize equipment to avoid breeding of diseases. This can be done using a UV or ozone treatment system.
Staffs, cleaning personnel and equipment should be disinfected regularly to keep the system clean and free from diseases.

Recirculating Aquaculture System

Types Of Recirculating Aquaculture system

There are basically two special types of RAS you should know.

  1. Aquarium
  2. Aquaponics

Summary on Recirculating aquaculture system

Here as promised from the first paragraph are things you should know about recirculating aquaculture system.

Kindly share and tell us what more you think we should know about RAS.

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