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Recirculating Aquaculture System :- RAS Fish Farming

 RECIRCULATING AQUACULTURE SYSTEM

Recirculating aquaculture system or RAS is a fish farming method in which we rearing fishes in fully controlled environment for large amount of production in small land area where water exchange is very limited. Filtration system are used to reducing the toxicity of water. By which we provide suitable habitat for the fishes like Catfish, Tilapia and some other fish species. Currently aquaculture is one of the fastest growing field in agriculture because of the growing demand of protein rich food in India.


Table of Contents:-


WHAT IS RECIRCULATING AQUACULTURE SYSTEM? 

This recirculating aquaculture system is completely based on small land area in which we sale fishes in whole year with good profit. In this System, first of all we use freshwater from borewell to fill our fish tanks, by which that cultured water is completely circulated from fish tank to Filtration system for their purification thereafter returned back to those fish tanks. Almost we can say these system is a completely closed circuit. In this cultured water, fishes produces metabolic wastes like fecal solids, solid waste, ammonia and CO2 etc. These wastes products(sludge) are either removed or converted into less-toxic products by the Filtration system components. Now purified water is returned back to fish tanks with sufficient amount diffused Oxygen in water. By recirculating purified water, water is now absolute limited with energy requirements. However it is not possible to design a completely closed recirculating system. Very less amount of water is required to run this recirculating aquaculture system because non-degradable wastes must be removed and evaporated that's why we replace some amount of water from this system. But still we are capable of using more then 90% of water from our recirculating system. Now water purification is done by filtration system consist of number of components with their specific functions, these components are like Mechanical filter, Bio-filter, UV filter and many more. Now we are going to elaborate these components with full detailing of Recirculating aquaculture System technology. By which we say this system is capable of perfectly removing of Ammonia, CO2 and maintaining the pH of water. 


Overview of Recirculating Aquaculture System posted by TANK FISH Kasta


BENEFITS/ADVANTAGES OF RECIRCULATING AQUACULTURE SYSTEM FISH FARMING:

RAS method has so many advantages in compared to biofloc or traditional open pond culture. If we do this RAS system on commercially, it can be very good way of earning some extra cash and income.


  • The most important benefits is that, in this, maximum production of fishes in limited source of water and land.
  • Fully controlled environment for the fish, We can completely control the environmental issues like climate and atmospheric issues like pollutants and many more, which can be controlled like diseases, parasites, predation, fish stress, and seasonally suboptimal growing conditions.
  • Optimal feeding strategy, Fishes eat sufficient amount of feed with good quality of branded feed not once with twice or thrice a day without any issues like environmental, diseases, or germs.
  • Easy grading and harvesting of fish, fishes cultured in separate-separate tank by which its going easy to classify all fishes in tank one by one without any disturbance to other fish of tanks and harvesting is also very easy to sale these fishes by one by one tanks.
  • Fully controlled from diseases, pathogens, algae, etc.


CONSTRAINS/DISADVANTAGES OF RECIRCULATING AQUACULTURE SYSTEM FISH FARMING:

If we want to grow out, RAS method has so many constraints/disadvantages in compared to biofloc or traditional open pond culture in respect of infrastructure, feeds and staff.


  • This system is very expensive related to other system to develop(building, tanks, biofilter, plumbing, filtration system) and to operate(pumping, aerating, heating, lighting, CCTVs) and has a high risk factor, need huge capital investment and high operating costs. 
  • Necessity of electricity 24*7 hr, if mechanical or electricity failure, which may lead to fish loss,when rearing of fish in huge density in small volume of water.
  • Technically skilled staff able to work in this systematic environment for management, very skilled support is required for managing and maintaining this complex system components like water circulation, biofilter system, and conduct water quality analysis.
  • Good water source from borewell, 
  • This RAS system is at very high risk, need to maintain fail-safe emergency alarms and backup power and pump system. We have to be very quick(15 minutes or less) in taking reaction in this system.

If we want to grow Recirculating aquaculture system, have to made beside or in cities, with good availability of electricity. Next to this, RAS technology is the best way of cultivating(farming) tropical fish species in summer or winter season.


 EQUIPMENTS REQUIRED FOR RECIRCULATING AQUACULTURE SYSTEM:

A basic RAS method consists of the following components:

  • Fish Tank
  • Mechanical Filter
  • Sedimentation Filter
  • Drum Filter
  • Biological Filter
  • BioTower/Degassing Tower
  • Moving Bed Filter
  • Denitrification
  • Oxygenation/Aeration Devices
  • UV disinfection
  • Ozone disinfection
  • Monitoring/Grading system
  • Feeding

Flowchart of RAS method by TANK FISH Kasta

Now, we are discussing these main points which are need to know for their use.

FISH TANKS:

Its main component of  recirculating aquaculture system where fishes are cultured in water. these may be made of Tarpaulin or Concrete. Life span of tarpaulin is 3-4 year but concrete has 15-20 times more than tarpaulin.


Tarpaulin tanks of recirculating system.


MECHANICAL FILTER:

In RAS system, the mechanical filter are used to remove or filter the solid metabolic waste from the fish tank. Now a days, this system have an outlet at bottom with a filter known the micro screen of mesh (size 40 to 100 microns). These solid waste are mainly faecal matter of fishes, need to removed/flushed out from tank for maintaining water quality/parameters. By this reduction of load on these filtration systems. Depending on the condition of water quality we choose either sedimentation filter or drumfiter.


Mechanical Filter System 



SEDIMENTATION FILTER:

The water flowing from mechanical filtration is lead to the sedimentation tank. In this tank, solid particles(non-soluble) are filtered/removed from flowing water using natural gravity.In this tank, polypropylene filter is properly packed. solid wastes/particles are settled down on this filter. At the bottom, these settled particles form a layer in sedimentation tank. These are regularly removed from this tank because they are very biologically active, in couple of hour nitrate produces nitrogen gas with the help of denitrifying bacteria in biofilter. After this treatment, the system water is moving for next filtration.


Man cleaning a Sedimentation filter

DRUMFILTER:

In this component, water are coming from following filtration stages, can also be mechanically cleaning process using a drum filter. Solid present in flowing water  are continuously and automatically removed therefore this component (drum filter) is not required daily maintenance . Bottom of drum filter needs continuous electricity. From this component water flows continuously which has  a filter screen (blue arrow).particles of flowing water blocked the filter screen. By clogging of filter screen water level uprises, Result of that, flushing mechanism is used to put in it. Finally drum rotates from outside, a spray nozzle with high pressure is used to clean that screen, and flushes the waste particles from the filter screen. Together water and waste particles are discarded in the gutter.


Example of installed DrumFilter Device on site


Explanation of Drum Filter Device


Inside DrumFilter


BIOLOGICAL FILTER:

Ammonium ion (NH4)is primarily metabolic wastes produced by fish during digestion of the feed, and also by uneaten feed,dead and decaying algae or fishes, which are settled down in fish tanks thereafter if temperature rises in water then these sludge (uneaten feed, dead algae/fishes) breakdown into ammonia. The ammonium ion is toxic, irritating and poisonous for fishes. Ammonium ion are used by some bacteria for energy production which present in biotower of recirculating system, and converted NH4 into nitrites. Ammonium and nitrite are less toxic at lower levels but  problems causes at this levels. In this filter, nitrite also transfer into nitrate (NO3). 

Biological Filtration System


BIOTOWER/DEGASSING TOWER:

In this tower, flowing water is pumped in the bio tower, polypropylene filter blocks in biofiltration is present. At the top of tower, water is spread over the filter materials. These water is flows through the filter packs of the biotower and then directly back into the flowing water. on the surface of the biofilter pack, a very thin biofilm layer of nitrifying bacteria is formed. This component is also used in recirculating system for removing dissolved gasses (i.e. CO2) from the cultured water. In that  case, we called it Degassing tower.

Bio-Tower Device

Degassing Tower Device

MOVING BED FILTER:

These moving bed filter is also a biological filter, which have a huge filter capacity with low volume. This component has a tank with aeration system and filled with filter beads (many shape and sizes are available). On the surface of the bead, a biofilm nitrifying bacteria grows which are used in biotower. 

Moving Bed Filter Device

DENITRIFICATION:

Every thing is given in denitrifying flowchart.

 
Denitrification flowchart of recirculating system

OXYGENATION/AERATION SYSTEM:

Aeration devices are used for maintaining the oxygen level in water of fish tanks by which fsh farmers rears more fish in small space. Those tanks which carrying huge amount of fish should be able to replace oxygen in every 20 to 30 minute. Blowing air through submerged pipes in the tanks is commonly used by most of fish farmers, if we supply sufficient amount of air in tank, there is no need of removal of Carbon dioxide (CO2). We  should have a backup plan for Aeration systems/devices.


Root Blower of Aeration/Oxygenation System

UV-C DISINFECTION:

UV-C light is used for thi antiseptic and germicidal effect. With the help of UV-C light, in running water and contaminated surface, it is possible to control/kill excessive growth of microorganisms including bacteria, fungi, and viruses. Before UV disinfection, water should be cleaned and free from small particles even at low dosages.


UV Disinfection Device

OZONE DISINFECTION:

Ozonation is quite similar to UV disinfection




MONITORING and CONTROLLING:

Fish farming can be properly done only when monitoring and controlling is done by itself not by labour. We have to check all the water parameters once a week for better growth of fishes. Farming is not a easy task, specially RAS system, in which we have to check all parameters like oxygen level. pH level, ammonia level, DO, CO2 and other levels and we have to recognise the behavior and movement of fishes by which we understand the problems of the fishes. So we have to very careful about fish farming.


GRADING SYSTEM:

On fish harvesting, we need to grade them according to their sizes. Grading is done by grading equipment or hand, it sort them based on their sizes. It help in making good profit on selling large fishes to the wholesalers.


FEEDING:

Feeding is very important factor for fishes. We have to provide feed according to the fish body weight, growth and activities of the fishes. Always try to feed our fishes with high quality of feed which has best nutritional value (includes protein, fat, carbohydrates, vitamins and minerals). These compound must be present in feed pellets  either we use commercial feed or homemade feed pellets. On average, if we feed our fishes what is the percentage of feed in there diet? we have to ate our fishes 3-7%  feed of there total body weight. Feed percentage depends on the fish size and weight. On fingerling (approx 5gm) feed should be given 6-7% to the fishes. Onwards size and weight of the fishes increases gradually feed percentage decreases. At last, when size of fish is about to 300gm then we provide feed to the fishes approx 3-4% of total body weight. After that we continue same percentage until harvesting. 


ABIS Feed for feeding

CONCLUSION OF RECIRCULATING AQUACULTURE SYSTEM:

This system is the best method for fish farming compared to traditional open fish farming. If in this method, we properly manage filtration process in which we save about to 90% of water then reuse it for culturing our fishes in tanks. RAS is used to culture fishes like Pangasius, tilapia, kwai as well other variety of catfish. A Recirculating fish farming system has many components like 24*7 hr Electricity, Emergency Generator, three Phase Electricity, Water facility, Pumphouse, Bulk Feed storage, Aeration System, Building and Recirculation Components, these are required for managing the whole RAS system site and System components. Proper management of farming water in tanks enhances the production of fishes at the time of harvesting. Major components which are present in farming water are nutrients or toxicants like ammonia, CO2, pH, pathogens etc. We have to filter/remove these compound from  the water, for better farming with the help of ecological engineering. This recirculating system has greater efficiency and productivity of fishes. When we use ecological engineering principle for treatment of pollutant water is reduces its working cost. Fish culture system have large volumes of fish production and returning back very less water wastage. Currently, aquaculture is new field and fastest growing segment because of very high demand of protein rich food and farming fishes on commercially, it can be greater source of earning/generating some extra income/money.


Good luck and may god bless you with your fish farming.


TANK FISH KASTA

EK KADAM FISH FARMING KI OOR

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