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1. HISTORY AND GENERAL VIEW OF AQUACULTURE :

Aquaculture in India has a long history, with references to fish culture in Kautilya's
Arthashastra (321–300 B.C.) and King Someswara's Manasoltara (1127 A.D.). The
traditional practice of fish culture in small ponds in eastern India is known to have
existed for hundreds of years; significant advances were made in the State of West
Bengal in the early nineteenth century with the controlled breeding of carp in
bundhs (tanks or impoundments where riverine conditions are simulated). Fish
culture received notable attention in the state of Tamil Nadu (formerly Madras) as
early as 1911, and subsequently, states such as Bengal, Punjab, Uttar Pradesh,
Andhra Pradesh and Telangana has initiated fish culture through the establishment
of Fisheries Departments and support to fishers and farmers for expansion of the
sector.

1.1 INTRODUCTION OF AQUACULTURE IN INDIA :

At the World Food Summit organized by the Food and Agriculture Organization
(FAO), the participating countries committed to reduce the number of malnour-
ished people in the world. It is a well-known fact that fish is rich in protein and essen-
tial amino acids. It is also a good source of calcium, vitamin A and B12 and omega-3
fatty acids. People irrespective of age who do not get sufficient nutrients from cere-
al-based diets, would be benefited from the inclusion of fish in the diet. Aquaculture
not only supplies dietary essentials for human consumption, but provides excellent
opportunities for employment and income generation, especially in the more eco-
nomically backward rural areas.

Fisheries in India is a very important economic activity and a flourishing sector with
varied resources and potentials. Only after the Indian Independence, has fisheries
together with agriculture been recognized as an important sector. India is also an
important country that produces fish through aquaculture in the world. India is
home to more than 10 percent of the global fish diversity. Presently, the country
ranks second in the world in total fish production with an annual fish production of
about 9.06 million metric tons.

Table 1.1: Fish Production in India for the period 1980-81 to 2019-20

Year Fish production (In Lakh Tonnes) Annual Average Growth Rate (Percent)

1980-81 Marine Inland Total Marine Inland All India
15.55 8.87 24.42 4.22 4.6 4.36

1981-82 14.45 9.99 24.44 -7.07 12.63 0.08

1982-83 14.27 9.4 23.67 -1.25 -5.91 -3.15

1983-84 15.19 9.87 25.06 6.45 5 5.87

1984-85 16.98 11.03 28.01 11.78 11.75 11.77

1985-86 17.16 11.6 28.76 1.06 5.17 2.68

1986-87 17.13 12.29 29.42 -0.17 5.95 2.29

1987-88 16.58 13.01 29.59 -3.21 5.86 0.58

1988-89 18.17 13.35 31.52 9.59 2.61 6.52

1989-90 22.75 14.02 36.77 25.21 5.02 16.66

1990-91 23 15.36 38.36 1.1 9.56 4.32

1991-92 24.47 17.1 41.57 6.39 11.33 8.37

1992-93 25.76 17.89 43.65 5.27 4.62 5

1993-94 26.49 19.95 46.44 2.83 11.51 6.39

1994-95 26.92 20.97 47.89 1.62 5.11 3.12

1995-96 27.07 22.42 49.49 0.56 6.91 3.34

1996-97 29.67 23.81 53.48 9.6 6.2 8.06

1997-98 29.5 24.38 53.88 -0.57 2.39 0.75

1998-99 26.96 26.02 52.98 -8.61 6.73 -1.67

1999-00 28.52 28.23 56.75 5.79 8.49 7.12

2000-01 28.11 28.45 56.56 -1.44 0.78 -0.33

2001-02 28.3 31.26 59.56 0.68 9.88 5.3

2002-03 29.9 32.1 62 5.65 2.69 4.1

2003-04 29.41 34.58 63.99 -1.64 7.73 3.21

2004-05 27.79 35.26 63.05 -5.51 1.97 -1.47

2005-06 28.16 37.56 65.72 1.33 6.52 4.23

2006-07 30.24 38.45 68.69 7.39 2.37 4.52

2007-08 29.2 42.07 71.27 -3.44 9.41 3.76

2008-09 29.78 46.38 76.16 1.99 10.24 6.86

2009-10 31.04 48.94 79.98 4.23 5.52 5.02

2010-11 32.5 49.81 82.31 4.7 1.78 2.91

2011-12 33.72 52.94 86.66 3.75 6.28 5.28

2012-13 33.21 57.19 90.4 -1.51 8.03 4.32

2013-14 34.43 61.36 95.79 3.67 7.29 5.96

2014-15 35.69 66.91 102.6 3.66 9.04 7.11

2015-16 36 71.62 107.62 0.87 7.04 4.89

2016-17 36.25 78.06 114.31 1.14 8.63 6.12

2017-18 37.56 89.48 127.04 3.61 14.62 11.13

2018-19 38.53 97.2 135.73 2.58 8.62 6.84

2019-20 37.27 104.37 141.64 -3.2 7.37 4.35

Source: Department of Fisheries, States Government / UTs Administration

As the second largest country in aquaculture production, the share of inland fisher-
ies and aquaculture has gone up from 46 percent in the 1980s to over 85 percent in
recent years in total fish production. Freshwater aquaculture showed an overwhelm-
ing ten-fold growth from 0.37 million tons in 1980 to 14.36 million tons in 2020; with a
mean annual growth rate of over 7 percent. Freshwater aquaculture contributes to
over 95 percent of the total aquaculture production. The freshwater aquaculture
comprises of the culture of carp fishes, culture of catfishes (air breathing and
non-air breathing), culture of freshwater prawns, culture of Pangasius, and culture
of tilapia.

In addition, in brackish water sector, the aquaculture includes culture of shrimp vari-
eties mainly, the native giant tiger prawn (Penaeus monodon) and exotic white leg
shrimp (Penaeus vannamei). Thus, the production of carp in freshwater and
shrimps in brackishwater form the bulk of major areas of aquaculture activity. The
three Indian major carps, namely catla (Catla catla), rohu (Labeo rohita) and
mrigal (Cirrhinus mrigala) contribute the bulk of production to the extent of 70 to 75
percent of the total fresh water fish production, followed by silver carp, grass carp,
common carp, catfishes forming a second important group contributing the
balance of 25 to 30 percent

The developmental support provided by the Indian Government through a network
of Fish Farmers' Development Agencies and Brackish water Fish Farmers' Develop-
ment Agencies and the research and development programmes of the Indian Coun-
cil of Agricultural Research (ICAR) have been the principal vehicles for this revolu-
tionary development. In addition, additional support was also provided by various
state governments, host of organizations and agencies like the Marine Products
Export Development Authority, financial institutions, etc.

India ranks second in the world inland fish production, next to China. China, with one
fifth of the world’s population, accounts for one¬ third of the world’s reported fish
production and two thirds of the worlds reported aquaculture production. It is
because, the Indian fresh water aquaculture system mostly revolves around 3 to 6
species combination based composite carp culture; whereas in China, farmers
stock as much as 10 or more compatible fish species in a single pond so as to effec-
tively and efficiently utilize all the available feeding zones, feeding niches / sub
niches and carrying capacity of the pond for optimizing the fish growth and produc-
tivity.

1.2 Fish Species Diversity in India

India is one of the rich biodiversity country having two biodiversity hotspots, namely
the Western Ghats and the Eastern Himalayas. The major inland aquatic resources
include 2.38 million ha of freshwater ponds and tanks, 1.2 million ha of brackish
water area and 3.15 million ha of reservoirs, besides about 0.19 million kilometers of
rivers and canals. Further, the large and medium dams have created almost 250
million cubic meters of water storage intercepting 30% of the available surface flow.
The long coastline of 8129 km with the exclusive economic zone (EEZ) encompasses
2.02 million km of coastal and offshore areas in eastern, western and southern parts
of India. Out of the known fish species of the world, India harbours approximately 10%
of them. Database of ICAR¬ National Bureau of Fish Genetic Resources (NBFGR) con-
tains 2,868 indigenous species of which 877 species are found in freshwaters, 113 in
brackish water and 1,878 in marine water, which belong to 39 orders, 225 families
and 852 genera (NBFGR, 2015).

2. RAS (RE-CIRCULATORY AQUACULTURE SYSTEM)

2.1 INTRODUCTION:

Recirculating Aquaculture Systems (RAS) consist of an organized set of processes
that allows at a least portion of the water leaving a fish culture tank to be recondi-
tioned and then reused in the same fish culture tank or other fish culture tanks

Recirculating systems for holding and growing fish have been used by fisheries
researchers for more than three decades. Attempts to advance these systems to
commercial scale of fish production have increased dramatically in the last decade
although few large systems are in operation. The interest in RAS is due to the advan-
tages such as greatly reduced land and water requirements in places where the
water resources are limited. Recirculating aquaculture systems (RAS) are
land-based aquaculture facilities – either open air or indoors – that minimize water
consumption by filtering, adjusting, and reusing the water. Compared to traditional
pond or open water aquaculture, the water recirculation process in RAS makes it pos-
sible to control the culture conditions and collect waste. In addition, land-based
aquaculture avoids escapees and limits external transmission of diseases and para-
sites.

RAS gives promise of more sustainable food production with healthier fish, lower con-
sumption of fresh water, and shorter transport distances, where fish can be grown
closer to the markets. By controlling the culture conditions, aquaculture production
in a RAS facility can be established almost anywhere, regardless of local conditions.

But, the RAS also have disadvantages, but the most important is the deterioration of
the water quality if the water treatment process within the system are not controlled
properly, and it can cause negative effects on fish growth, increase the appear risk
of infectious disease, increase fish stress, and other problems associated with water
quality that resulting in deterioration of fish health and consequently loss of produc-
tion. The water quality in RAS depends on different factors such as the source, the
level of recirculation, the species have been cultured and the waste water treatment
process within the system.

Most water quality problems experienced in RAS were associated with low dissolved
oxygen (D.O) and high fish waste metabolite concentrations in the culture water.
Waste metabolites production

include Total Ammonia Nitrogen (TAN), unionized ammonia (NH3-N), Nitrite
(NO2-N), Nitrate (NO3-N) (to a lesser extent), and Dissolved carbon dioxide (CO2),
Total Suspended Solids (TSS), and Non-biodegradable organic matter. However,
maintaining good water quality conditions is of primary importance in any type of
aquaculture system, especially in RAS.

A recirculatory aquaculture model is a closed system. It combines of fish tanks, filtra-
tion and water treatment systems. The fish are housed in tanks and therefore the
water is exchanged continuously which guarantees and consists of optimum grow-
ing conditions.

Water flows by pumping out into the tanks, through biological and mechanical filtra-
tion systems then returned into the tanks. Therefore, no complete water exchange,
rather only 5% to 10% water rate of exchange takes per day is being done.

Recirculating the aquaculture system is the key to the future of aquaculture. It
makes sustainable use of the water resources, and in places where there is a scarci-
ty of good quality water.

Even though it has a high establishment cost, but the scope of RAS is vast. It is envi-
ronment friendly, there is control over the production, and the supply can meet the
demand according to the market conditions.

There is low pollution to the surroundings in recirculating aquaculture systems.

2.2 Critical production considerations :

All aquaculture production systems must provide a suitable environment to
promote the growth of the aquatic crop. Critical environmental parameters include
the concentrations of dissolved oxygen, un-ionized ammonia-nitrogen, nitrite-nitro-
gen, and carbon dioxide in the water of the culture system. Nitrate concentration,
pH, and alkalinity levels within the system are also important. To produce fish in a
cost effective manner, aquaculture production systems must maintain good water
quality during periods of rapid fish growth. To ensure such growth, fish

are fed high-protein pelleted diets at different rates. Feeding rate, feed composition,
fish metabolic rate and the quantity of wasted feed affect tank water quality. As
pelleted feeds are introduced to the fish, they are either consumed or left to decom-
pose within the system.

The by-products of fish metabolism include carbon dioxide, ammonia-nitrogen,
and fecal solids. If uneaten feeds and metabolic by-products are left within the
culture system, they will generate additional carbon dioxide and ammonia-nitro-
gen, reduce the oxygen content of the water, and have a direct detrimental impact
on the health of the cultured product.

In aquaculture ponds are prepared with proper environmental conditions which are
maintained by balancing the inputs of feed with the assimilative capacity of the
pond. The pond’s natural biological productivity (algae, higher plants, zooplankton
and bacteria) serves as a biological filter that processes the wastes. As pond produc-
tion intensifies and feed rates increase, supplemental and/or emergency aeration
are required. At higher rates of feeding, water must be exchanged to maintain good
water quality.

The carrying capacity of tank systems must be high to provide for cost-effective fish
production because of the higher initial capital costs of tanks compared to earthen
ponds. Because of this expense and the limited capacity of the “natural” biological
filtration of a tank, the producer must rely upon the flow of water through the tanks
to wash out the waste by-products. Additionally, the oxygen concentration within
the tank must be maintained through continuous aeration, either with atmospheric
oxygen (air) or pure gaseous oxygen

2.3 Recirculating systems design :

Generally, a fish production system is designed to meet a predetermined produc-
tion capacity, expressed as pounds (kg) fish produced per year. To maximize its
efficiency, the production system must be operated at or near its maximum carry-
ing capacity defined by the maximum pounds that can be supported by the system.
Therefore,

the starting point for a rigorous design of a recirculating aquaculture system begins
by determining the system’s carrying capacity.

The principle components of the recirculating system design described here
include: a micro screen filter for solids removal; a fluidized reactor for bio filtration; a
cascade column for both aeration and carbon dioxide stripping; a unit for purified
oxygen injection multi-stage low head oxygenator or U-tube); and a circular tank
for fish culture. The recirculating aquaculture system design also requires methods
to add ozone and manage PH

2.4 Methodological approach :

The study was conducted in three stages. The first stage was a desk analysis of stud-
ies, projects and initiatives, as well as a mapping of available data sources. Stage
two consisted of interviews with industry stakeholders to complement the desk anal-
ysis and the data collected from publicly available sources. In the third stage, three
case studies were developed to analyze the RAS production of some relevant spe-
cies.

3. Other elements:

3.1 Tanks: The environment in the fish rearing tank must meet the needs of the fish,
both in respect of water quality and tank design. Choosing the right tank design,
such as size and shape, water depth, self-cleaning ability, etc. can have a consider-
able impact on the performance of the species reared. The different factors must be
assessed and optimized in the design of a specific RAS system.

If the fish is bottom dwelling, the need for tank surface area is most important, and
the depth of water and the speed of the water current can be lowered (turbot, sole
or other flatfish), whereas submersed living species such as salmonids will benefit
from larger water volumes and show improved performance at higher speeds of
water.

In a Circular tank, or in a square tank with cut corners, the water moves in a circular
pattern making the whole water column of the tank move around the center. The
organic particles have a relatively short residence time of a few minutes, depending
on tank size, due to this hydraulic pattern that gives a self-cleaning effect. A vertical
inlet with horizontal adjustment is an efficient way of controlling the current in such
tanks.

In a Raceway the hydraulics have no positive effect on the removal of the particles.
On the other hand, if a fish tank is stocked efficiently with fish, the self-cleaning
effect of the tank design will depend more on the fish activity than on the tank
design. The inclination of the tank bottom has little or no influence on the self-clean-
ing effect, but it will make complete draining easier when the tank is emptied.

A hybrid tank type between the circular tank and the raceway called a “D-ended
raceway” also combines the self-cleaning effect of the circular tank with the
efficient space utilization of the raceway. However, in practice this type of tank is
seldom used, presumably because the installation of the tank requires extra work
and new routines in management.

Figure 3.1 Circular tank, D- shaped tank type and Raceway Tank

Tank outlets must be constructed for optimal removal of waste particles, and fitted
with screens with suitable mesh sizes. Also, it must be easy to collect dead fish
during the daily work routines.

Tanks are often fitted with sensors for water level, oxygen content and temperature
for having complete control of the farm. It should also be considered to install diffus-
ers for supplying oxygen directly into each tank in case of an emergency situation

Tank Circular tank D-ended Raceway type
properties raceway

Self-cleaning effect 5 4 3

Low residence time 5 4 3
of particles

Oxygen control and 5 5 4
regulation

Space 24 5
utilization

Table3.1 Different tank designs give different properties and advantages. Rating 1-5, where 5 is the best.

3.2 Mechanical filtration

Mechanical filtration of the outlet water from the fish tanks has proven to be the only
practical solution for removal of the organic waste products. Today almost all recir-
culated fish farms filter the outlet water from the tanks in a so called micro screen
fitted with a filter cloth of typically 40 to 100 microns. The drum filter is by far the most
commonly used type of micro screen, and the design ensures the gentle removal of
particles.

Function of the drum filter:
1. Water to be filtered enters the drum.
2. The water is filtered through the drum’s filter elements. The difference in water
level inside/outside the drum is the driving force for the filtration.
3. Solids are trapped on the filter elements and lifted to the backwash area by the
rotation of the drum.
4. Water from rinse nozzles is sprayed from the outside of the filter elements. The
rejected organic material is washed out of the filter elements into the sludge tray
5. The sludge flows together with water by gravity out of the filter escaping the fish
farm for external waste water treatment.

Figure 3.2 Drum filter

Micro screen filtration has the following advantages :
• Reduction of the organic load of the bio filter.
• Making the water clearer as organic particles are removed from the water.
• Improving conditions for nitrification as the bio filter does not clog.
• Stabilizing effect on the bio filtration processes.

3.3 Bio- Filter (Biological treatment):

Not all the organic matter is removed in the mechanical filter, the finest particles will
pass through together with dissolved compounds such as phosphate and nitrogen.
Phosphate is an inert substance, with no toxic effect, but nitrogen in the form of free
ammonia (NH3) is toxic, and needs to be transformed in the bio filter to harmless
nitrate. The breakdown of organic matter and ammonia is a biological process
carried out by bacteria in the bio filter. Heterotrophic bacteria oxidise the organic
matter by consuming oxygen and producing carbon dioxide, ammonia and sludge.
Nitrifying bacteria convert ammonia into nitrite and finally to nitrate.

The efficiency of bio filtration depends primarily on:
• The water temperature in the system.
• The pH level in the system

To reach an acceptable nitrification rate, water temperatures should be kept within
10 to 35 °C (optimum around 30 °C) and pH levels between 7 and 8. The water tem-
perature will most often depend on the species reared, and is as such not adjusted
to reach the most optimal nitrification rate, but to give optimal levels for fish growth.
Regulation of pH in relation to bio filter efficiency is however important as lower pH
level reduces the efficiency of the bio filter. The pH should therefore be kept above 7
in order to reach a high rate of bacterial nitrifying. On the other hand, increasing pH
will result in an increasing amount of free ammonia (NH3), which will enhance the
toxic effect. The aim is therefore to find the balance between these two opposite
aims of adjusting the pH. A recommended adjustment point is between pH 7.0 and
pH 7.5.

Two major factors affect the pH in the water recirculation system:
• The production of CO2 from the fish and from the biological activity of the bio filter.
• The acid produced from the nitrification process.

The nitrifying process produces acid (H+) and the pH level falls. In order to stabilize
the pH, a base must be added. For this purpose lime or sodium hydroxide (NaOH) or
another base needs to be added to the water.

In general, ammonia is toxic to fish at levels above 0.02 mg/L. The maximum concen-
tration of TAN to be allowed at different pH levels if a level below 0.02 mg/L of ammo-
nia is to be ensured. The lower pH levels minimizes the risk of exceeding this toxic
ammonia limit of 0.02 mg/L, but the fish farmer is recommended to reach a level of
minimum pH 7 in order to reach a higher bio filter efficiency as explained. Unfortu-
nately, the total concentration of TAN to be allowed is thereby significantly. Thus
there are two opposite working vectors of the pH that the fish farmer has to take into
consideration when tuning his bio filter.

Nitrite (NO2-) is formed at the intermediate step in the nitrification process, and is
toxic to fish at levels above 2.0 mg/L. If fish in a recirculation system are gasping for
air, although the oxygen concentration is fine, a high nitrite concentration may be
the cause. At high concentrations, nitrite is transported over the gills into the fish
blood, where it obstructs the oxygen uptake. By adding salt to the water, reaching as
little as 0.3 ‰, the uptake of nitrite is inhibited.

Nitrate (NO3-) is the end-product of the nitrification process, and although it is con-
sidered harmless, high levels (above 100 mg/L) seem to have a negative impact on
growth and feed conversion. If the exchange of new water in the system is kept very
low, nitrate will accumulate, and unacceptable levels will be reached. One way to
avoid the accumulation is to increase the exchange of new water, whereby the high
concentration is diluted to a lower and trouble-free level.

Bio-filters are typically constructed using plastic media giving a high surface area
per m3 of bio-filter. The bacteria will grow as a thin film on the media thereby occu-
pying an extremely large surface area. The aim of a well-designed bio-filter is to
reach as high a surface area as possible per m3 without packing the bio-filter so
tight that it will get clogged with organic matter under operation. It is therefore
important to have a high

percentage of free space for the water to pass through and to have a good overall
flow through the bio-filter together with a sufficient back-wash procedure

Bio-filters used in recirculation systems can be designed as fixed bed filters or
moving bed filters. All bio-filters used in recirculation today work as submerged
units under water. In the fixed bed filter, the plastic media is fixed and not moving.
The water runs through the media as a laminar flow to make contact with the bacte-
rial film. In the moving bed filter, the plastic media is moving around in the water
inside the bio-filter by a current created by pumping in air. Because of the constant
movement of the media, moving bed filters can be packed harder than fixed bed
filters thus reaching a higher turnover rate per m3 of bio-filter. There is however no
significant difference in the turnover rate calculated per m2 (filter surface area) as
the efficiency of the bacterial film in either of the two types of filter is more or less the
same.

Figure 3.3(a) Moving bed in the bio-filter

In the fixed bed filter, however, fine organic particles are also removed as these sub-
stances adhere to the bacterial film. The fixed bed filter will therefore act also as a
fine mechanical filtration unit removing microscopic organic material and leaving
the water very clear.

There are several solutions for the final design of biofilter systems depending on
farm size, species to be cultured, sizes of fish, etc.

3.4 Degassing, aeration :

Before the water runs back to the fish tanks accumulated gases, which are detrimen-
tal to the fish, must be removed. This degassing process is carried out by aeration
of the water, and the method is often referred to as stripping.

The water contains carbon dioxide (CO2) from the fish respiration and from the bac-
teria in the bio-filter in the highest concentrations, but free nitrogen (N2) is also pres-
ent. Accumulation of carbon dioxide and nitrogen gas levels will have detrimental
effects on fish welfare and growth. Under anaerobic conditions hydrogen sulphide
(H2S) can be produced, especially in saltwater systems. This gas is extremely toxic
to fish, even in low concentrations, and fish will be killed if the hydrogen sulphide is
generated in the system.

Aeration can be accomplished by pumping air into the water whereby the turbulent
contact between the air bubbles and the water drives out the gases. The aeration
well system is however not as efficient for removing gases as the trickling filter
system, also called a degasser. In the trickling system, gases are stripped off by
physical contact between the water and plastic media stacked in a column. Water
is led to the top of the filter over a distribution plate with holes, and flushed down
through the plastic media to maximize turbulence and contact, the so called strip-
ping process.

3.5 Oxygenation :

The aeration process of the water, which is the same physical process as degassing
or stripping, will add some oxygen to the water through simple exchange between
the gases in the water and the gases in the air depending on the saturation level of
the oxygen in the water. Aeration of this water will typically bring the saturation up to
around 90%, in some systems 100% can be reached. Pure oxygen is often delivered
in tanks in the form of liquid oxygen, but can also be produced on the farm in an
oxygen generator.

Figure 3.5(a) Oxygen Cone for dissolving pure oxygen under high pressure

Figure 3.5(b) Sensor for Measuring Oxygen Saturation of the Water.

UV disinfection works by applying light in wavelengths that destroy DNA in
biological organisms. In aquaculture pathogenic bacteria and one-celled organ-
isms are targeted. The treatment has been used for medical purposes for decades
and does not impact the fish as UV treatment of the water is applied outside the fish
production area. It is important to understand that bacteria grow so rapidly in organ-
ic matter that controlling bacterial numbers in traditional fish farms has limited
effect. The best control is achieved when effective mechanical
filtration is combined with a thorough biofiltration to effectively remove organic
matter from the process water, thus making the UV radiation work efficiently.
The UV dose can be expressed in several different units. One of the most widely used
is micro Watt-seconds per cm2 (µWs/cm2). The efficiency depends on the size and
species of the target organisms and the turbidity of the water.

Figure 3.6 UV treatment Systems closed and open

3.7 PH Regulator/Sensor:

The nitrifying process in the bio-filter produces acid, thus the pH level will drop. In
order to keep a stable pH a base must be added to the water. In some systems a
lime mixing station is installed dripping limewater into the system and thereby stabi-
lizing pH. An automatic dosage system regulated by a pH-meter with a feedback
impulse to a dosage pump is another option. With this system it is preferable to use
sodium hydroxide (NaOH) as it is easy to handle and making the system easier to
maintain.

3.8 Water Temperature Regulation :

Maintaining an optimal water temperature in the culture system is most important
as the growth rate of the fish is directly related to the water temperature. Using the
intake water is a fairly simple way of regulating the temperature from day to day. In
an indoor recirculation system the heat will slowly build up in the water, because
energy in the form of heat is released from the fish metabolism and the bacterial
activity in the bio-filter. Heat from friction in the pumps and the use of other installa-
tions will also accumulate. High temperatures in the system are therefore often a
problem in an intensive recirculation system. By adjusting the amount of cool fresh
intake water into the system, the temperature can be regulated in a simple way.

If cooling by the use of intake water is limited a heat pump can be used. The heat
pump will utilize the amount of energy normally lost in the discharge water or in the
air leaving the farm. The energy is then used for cooling the circulating water inside
the farm.

3.9 PUMPS:

Different types of pumps are used for circulating the process water in the system.
Pumping normally requires a substantial amount of electricity, and low lifting
heights and efficient and correctly installed pumps are important to keep running
costs at a minimum.

The lifting of water should preferably occur only once in the system, whereby the
water runs by gravity all the way through the system back to the pump sump.
Pumps are most often positioned in front of the bio-filter system and the degasser
as the water preparation process starts here. In any case, pumps should be placed
after the mechanical filtration to avoid breaking the solids coming from the fish
tanks.

4. Monitoring, Control and Alarms :

Intensive fish farming requires close monitoring and control of the production in
order to maintain optimal conditions for the fish at all .times. Technical failures can
easily result in substantial losses, and alarms are vital installations for securing the
operation.

Whatever the case, no system will work without the surveillance of the personnel
working on the farm. The control system must therefore be fitted with an alarm
system, which will call the personnel if any major failures are about to occur. A reac-
tion time of less than 20 minutes is recommended.

Whatever the case, no system will work without the surveillance of the personnel
working on the farm. The control system must therefore be fitted with an alarm
system, which will call the personnel if any major failures are about to occur. A reac-
tion time of less than 20 minutes is recommended.

4.1 Water Intake :

Water used for recirculation should preferably come from a disease-free source or
be sterilized before going into the system. In most cases it is better to use water from
a borehole, a well, or something similar than to use water coming directly from a
river, lake or the sea

5. Species Of Fish Recommended for Re-Circulation:

A recirculation system is a costly affair to build and to operate. There is competition
on markets for fish and production must be efficient in order to make a profit. Select-
ing the right species to produce and constructing a well functioning system are
therefore of high importance. Essentially, the aim is to sell the fish at a high price and
at the same time keep the production cost at the lowest possible level.

Water temperature is one of the most important parameters when looking at the
feasibility of fish farming, because fish are cold blooded animals. This means that
fish have the same body temperature as the temperature of the surrounding water.
Fish cannot regulate their body temperature like pigs, cows or other farmed
animals. Fish simply do not grow well when the water is cold; the warmer the water,
the better the growth.

Another issue affecting the feasibility of fish farming is the size of the fish grown in
the farm. At any given temperature, small fish have a higher growth rate than large
fish. This means that small fish are able to gain more weight over the same period of
time than large fish. Small fish also convert fish feed at a better rate than large fish.
Growing faster and utilizing feed more efficiently will of course have a positive influ-
ence on the production costs as these are lowered when calculated per kilo of fish
produced.

Compared to other farmed animals there is a large variety of fish, and many differ-
ent fish species are farmed. In comparison, the market for pigs, cattle or chicken is
not diversified in the same way as fish. The consumer does not ask for different spe-
cies of pigs, cattle or chicken, they just ask for different cuts or sizes of cuts. But when
it comes to fish, the choice of species is wide, and the consumer is used to choosing
from a range of different fish, a situation which makes many different fish species
interesting in the eyes of any fish farmer.

The suitability of rearing specific fish species in recirculation depends on many differ-
ent factors, such as the profitability, environmental concerns, biological suitability.
In the tables below fish species have been grouped into different categories depend-
ing on the commercial feasibility of growing them in a recirculation system.

It should be mentioned that for small fish the use of recirculation is always recom-
mended, because small fish grow faster and are therefore particularly suited to a
controlled environment until they have reached the size for on-growing.

SUITABLE SPECIES

Species Suitability Water Kg per m3 Protein

Rohu, Katla Fair Warm, 55 kg per M3 36% protein
Rainbow Trout Freshwater 55 kg per M3 @ 3-5%
weight
Fair Warm,
freshwater 45%

[email protected]

Tilapia species Excellent Very warm water 55 - 75 kg 32% protein
per M3
fresh or brackish, @ 3.5%
fair water quality weight

Murrel & Korameenu Fair Warm, 55 kg per M3 42% protein
Fair Freshwater
Baitfish (shiners, @ 3-5%
minnows) Warm, weight
freshwater fair
water quality 75-100 kg per M3 32% protein
per gallon
CO 3-5%
weight

Good biological performance and acceptable market conditions make the following
fish interesting for production to market size in recirculation aquaculture :



5.1 FEED:

A lot of factors come into play when operating a recirculating aquaculture system
(RAS), but none are as important as feeding.
Not only is feeding fish stocks one the largest operating expenses when a RAS is up
and running, but accurate feeding calculations are vital when planning a new
system – even more so than with a flow-through aquaculture system.
When you think about a recirculating aquaculture system, it’s really processing the
feed more than its processing fish. Feeding is the thing you need to get a handle on
at the outset because it drives all the other calculations and determines your overall
water quality and system performance

Figure 5.1: Eating feed and using oxygen results in fish growth and excretion of waste products,
such as carbon dioxide, ammonia and faeces.

Fish feed should be selected according to the size of the fish. Fish feeds size ranging
from 0.5 mm to 4mm is available in the market today. We can see from the fish feed
chart and select feed size according to the size of fishes.

2. Protein contained in the Fish Feed.

When choosing a feed for the fish, the amount of protein in it should be taken into
consideration. High protein rich diet should be fed to juvenile fishes. As the fishes
grow, their protein intake can be reduced. Feeds with high protein content are more
expensive.
The feed with a size of 0.8 mm contains 38% protein. The feed of size 1.2 and 1.8 mm
contains 32% and the 3 mm and 4 mm fish feeds contain only 24% protein.

3. Average body mass of fish.

The weight of the fish determines the amount of feed to be given to the fish. The aver-
age body mass of a fish is the average weight of the fish growing in the fish pond. To
understand this you can catch 10 or 20 fishes from the fish pond and take its average
weight. For example, if the 10 fish we catch weigh one kilogram, its average body
mass is 100 grams.

4. Price of fish feed

In the recent times, there has been a sharp rise in the price of fish feed. Fishes in our
farm are fed with feed from the company called xxxxxxx. The price of fish feed
depends on the size of the feed as well as on the amount of protein contained in it.

6. Project planning :

The idea of building a recirculation fish farm is often based on very different views on
what is important and what is interesting. People tend to focus on things they
already know or things they find most exciting, and in the process forget about other
aspects of the project.

Five major issues should be addressed before launching a project:

• Sales prices and market for the fish in question.

• Site selection including licences from authorities.

• System design and production technology.

• Work force including a committed manager.

• Financing the complete project all the way to a running business.

6.1 Sales prices and market :

The very first thing is to find out if the fish can be sold at acceptable prices and in
sufficient volumes. It is therefore important to carry out a proper market survey
before further steps are taken. Fish prices in the shops are very different from the
prices you will receive ex farm. Bringing fish from the farm to display at the supermar-
ket is a long process involving procedures for killing, gutting, packing and transport.
The costs involved can be significant, and the costs must be included in the overall
calculations. The supermarket and so called middlemen will take their share of the
profit, and the loss in weight from gutting the fish will of course make a significant
difference in the final weight of the fish you are getting paid for

6.2 Site selection and licensing :

Selection of a good site is extremely important. Although recirculation technology
claims to be water saving the need for water in fish farming is obvious. Ground water
is by far the most preferred water source, because of its purity and relatively cold
temperature. Water taken directly from rivers, lakes or the sea is not recommended.
It is advisable to use borehole water. The site selection is also directly linked to the
work load when seeking approval from local, regional, or national authorities to
build a fish farm.

6.3 System design and technology :

Many fish farmers tend to design and build systems or solutions themselves, which
at first glance is understandable as you want to keep costs down and to have your
own ideas incorporated. The best solution is, however, to approach a professional
system supplier and discuss the ideas for the technology in mind, and find out
together the optimal solution for building the farm. The fish farmer should spend his
time operating and optimizing the fish farm operation instead of getting involved in
detailed technical solutions and design work. System suppliers most often work in a
very systematic way bringing the project afloat from basic design to construction
and final start-up of the farm. Some system suppliers even support day-to-day
farm management and operational procedures to ensure a proper hand-over and
long term success.

6.4 Work force :

Finding skilled employees is vital, so that the management of the farm can be well
taken care of. It is of utmost importance to find an overall operational farm manag-
er, who is fully committed to the job, wanting to succeed as much as the sharehold-
ers do. Fish are living creatures and require tight management on a daily basis to
grow in a healthy and sound environment. Mistakes or mismanagement will immedi-
ately have a huge impact on production and fish welfare. As the aquaculture indus-
try grows and become more professionalized the need for well-educated employ-
ees becomes evident. Training and education is increasingly becoming an import-
ant part of modern aquaculture.

6.5 Financing :

The requirement for financing of the complete project is often seriously underesti-
mated. The capital costs are very high when building and starting up a new fish
farm, and investors seem to forget that growing fish to market size requires
patience. The time from starting the construction and getting the first pay-back
from fish sold takes typically from one to two years. Cash flow is thus slow in the
beginning, and it is recommended to stock more fish into the system in the starting
phase and to sell off this excess number of fish at a smaller size in the first year until
the production logistics have reached the planned daily output of volumes and
sizes. In order to get a systematic overview of the whole project, a business plan
should be elaborated. It is beyond the scope of this guide to go into details on how
to write a business plan or how to conduct a market survey for that matter. Detailed
information on such subjects must be sought elsewhere. However, a draft business
plan and examples of budgets and financial calculations should be aware of the
challenges when setting up a fish farming project.

7. Running a recirculation system :

Moving from traditional fish farming to recirculation significantly changes the daily
routines and skills necessary for managing the farm. The fish farmer has now
become a manager of both fish and water. The task of managing the water and
maintaining its quality has become just as important, if not more so, than the job of
looking after the fish. The traditional pattern of doing the daily job on a traditional
flow-through farm has changed into fine tuning a machine that runs constantly 24
hours a day. Automatic surveillance of the whole system ensures that the farmer
has access to information on the farm at all times, and an alarm system will call if
there is an emergency.

8. Routines and procedures :

The most important routines and working procedures are listed below. Many more
details will occur in practice, but the overall pattern should be clear. It is essential to
make a list with all the routines to be checked each day, and also lists for checking
at longer intervals.

8.1 Daily or weekly :

• Visually examine the behavior of the fish.
• Visually examine the water quality (transparency/turbidity).
• Check Water flow in tanks.
• Check and Note the distribution of feed from feeding machines.
• Remove and register dead fish.
• Wipe off membrane of oxygen probes.
• Registration of actual oxygen concentration in tanks.
• Check water levels in pump sumps.
• Check nozzles spraying on mechanical filters.
• Registration of temperature.
• Make tests of ammonia, nitrite, nitrate, pH.
• Registration of volume of new water used.
• Check pressure in oxygen cones.
• Check NaOH or lime for pH regulation.
• Control that UV-lights are working.
• Register electricity (kWh) used.
• Make sure the alarm system is switched on before leaving the farm.

8.2 Weekly or monthly :

• Clean the bio filters according to the manual
• Check water level in buffer tank
• Check amount of remaining O2 in oxygen tank (if we installed)
• Check the valuations of pH-meter
• Assessment of feeders
• Calibrate O2 probes in fish tanks and system
• Check alarms – make alarm tests
• Check that emergency oxygen works in all tanks
• Check all pumps and motors for failure or dissonance
• Check generators and make a test-start
• Grease the bearings of mechanical filters
• Rinse spray bar nozzles on mechanical filters
• Check filter sumps - no sludge must be observed.

8.2 Weekly or monthly :

• Clean the bio filters according to the manual
• Check water level in buffer tank
• Check amount of remaining O2 in oxygen tank (if we installed)
• Check the valuations of pH-meter
• Assessment of feeders
• Calibrate O2 probes in fish tanks and system
• Check alarms – make alarm tests
• Check that emergency oxygen works in all tanks
• Check all pumps and motors for failure or dissonance
• Check generators and make a test-start
• Grease the bearings of mechanical filters
• Rinse spray bar nozzles on mechanical filters
• Check filter sumps - no sludge must be observed.

8.4 Disease :

For the innovative entrepreneur there are several opportunities in this kind of recy-
cled aquaculture. The example of combining different farming systems can be
developed further into recreational businesses. There are many examples of recircu-
lation systems operating without any disease problems at all. In fact, it is possible to
isolate a recirculation fish farm completely from unwanted fish pathogens. Most
important is to make sure that fish stocked in the facility are absolutely disease free.
Make sure that the water used is disease free or sterilized before going into the
system; it is far better to use water from a borewell, or a similar source than to use
water coming directly from the sea, river or lake. Also, make sure that no one enter-
ing the farm is bringing in any diseases, whether they are visitors or staff.

9. Conclusion :

The technology described consists of some of the most cost and technologically
effective unit processes available to recirculating systems. The system scale is
primarily limited to the amount of risk one is willing to place in a single recirculating
production module and the ability to manage the fish and the hydraulics in the fish
culture tank. Although recycle aquaculture systems have many advantages, the
systems have large capital investments and high operating expenses relative to
other production technologies.

Checklist to be used when implementing a recirculation system

1 Project information
Describe aim and goal of the project
Species to be farmed
Production per year, in tonnes.
Size of fish in / out - production plan
Number of batches per year
Estimate of Feed Conversion Rate (FCR)
Existing drawings or other information available
Has discharge permission been granted?
Restrictions, consent levels, etc.
Available farm manager or fish specialist
Other vital information, special problems, etc.

2 Site information
Is it saltwater or freshwater?
Available water source.
Seawater, river, well, ground water, borehole
How much water is available? Liters.
Water temperature. Summer / winter
Day / night fluctuations
Water analysis.
Results pH
Weather conditions, max / min air temperature
Hard winters, extreme summer heat, etc.
Building ground conditions
Ground area available Shape of building area
Available space for waste water treatment
Settlement ponds/ sump etc.
Local power supply, specify

3
Nursery / First feed
Pre Grow-out / Fry
GCroonwt-eonutt of facility
Broodstock
Live feed production
Quarantine unit – in Acclimatization unit – out
Water intake treatment
Waste water treatment
Grading / Harvesting / Live Delivery
Laboratory / Workshop Office / Canteen
Emergency generator
Oxygen generator / Emergency oxygen tank
Water heating / Chilling system
Building requirements, Insulation
Architecture, Surroundings