TANK CULTURE

By : P.Shobiya, S.Saruga & A.SasitharanUniversity of Jaffna

Out line• Introduction on tank

aquaculture

• Tank design and construction

• Shapes of tanks

• Seasonal aquaculture tank

• Tanks can be manufactured from a variety of materials such as wood, concrete, metal, plastics, poly-ethylene, PVC, fiber-glass etc.

• An infinite number of shapes and sizes to suite the specific needs of the species and farming operation.

The recommended characteristics for, aquaculture tanks are as follows

The interior surface should be smooth to prevent abrasion. The surfaces should be nontoxic. The tanks should be durable and portable, should have long life, ease of cleaning, easy to sterilize. It should be non-corrosive affordable.

Tanks are commonly used for:

1) fry production

2) as temporary holding facilities for fingerlings, brood stock or

3) food fish ready for sale.

4) aquarium fish production

5) a public display aquaria.

• Tanks are becoming popular especially for intensive production

systems e.g. Catfish farming

Tank culture has now become more attractive because of the following factors; …

1) Tanks are used in aquaculture research.

2) Ponds require relatively large land area compared to tanks systems

3) Experimental parameters are more easily controlled tanks than in ponds.

4) Tanks are made in large numbers by manufacturers, using different materials.

Tank design and construction

• Materials used

• Tanks are made from:

1) wood,

2) concrete,

3) plastic,

4) fiberglass,

5) metal,

6) glass.

Wooden tanks

• They are cheap • Light in weight • Easy to work with. Plywood may be used. • Do not use treated wood because it may be toxic to fish. • All surfaces should be painted to protect the wood. • Do not use paints that have lead as this would leach into

the water. • The interior of the tank should be covered with non-toxic

materials such as epoxy or fiberglass resin paint. • They cure in about 2 days, forming a hard and smooth

surface. • Water proof liners may also be used in wooden tanks

Concrete Tanks

• Concrete is used for large tanks or pools.

• Tanks can also be made from gunite which is strong, durable, compact, but is more expensive than liners

Plastic Tanks

• Plastic includes polypropylene, polyethylene, poly butylene, polyvinyl chloride (PVC), acrylics, and vinyl.

• Each one has its own bad and good qualities.

Advantage of plastic tanks include the following:

• it is light weight,

• portable,

• repairs are easier,

• can be made in various shapes and sizes,

• most are non-toxic.

Fiberglass is mostly chosen for aquaculture for tank construction because of the following factors:

• it is light weight,

• strong,

• durable,

• inert

• can withstand the effects of UV rays.

Shapes of tanks

Circular, rectangular, square and oval tanks

(a) Circular Tanks .commonly used for nursery and grow out purposes also

used. .have better hydraulic characteristic, .The self cleaning action and oxygen distribution of circular

tank hold specific advantages .The velocity, circulation of water will cause

- better mixing of oxygen - food distributed - uniform water quality

.higher stock densities

(b) Square and Rectangular tanks . advantage of efficient use of space. . contribute to savings on construction costs. disadvantage that wastes tend to collect in the

corners,.. The corners of square or rectangular tanks are

therefore often rounded to improve the hydraulics and flow patterns.

c)Oval tanks . are an effort to combine the advantages of circular tanks & rectangular tank-efficient water use and self cleaning action of circular tank-the space efficiency of rectangular tanks.

. found in intensive indoor and outdoor systems, where advance aeration technology are applied

Water Inlet . control over the flow rate (L/sec) and velocity (cm/sec) of

water..The design must allow for the maintenance of flow

patterns to maintain the self cleaning action , minimize the risk of blockages .

. when using underground or lowly saturated water sources, the inlet can also be designed to facilitate with aeration of inlet water through the use of jets, diffusers

. adequate diameter for the inlet pipe should be maintained.

. maintain a proper balance between: Velocity and flow pattern The self cleaning function of the fish The energy requirements of the fish

. Velocity needs to be adapted according to species and size of fish.

Water Outlet and Flow Patterns

.Flow patterns are functions of water inlet and outlet design.

.The water outlet must also make provision to regulate operating depth of the tanks.

Tank Bottom and Drainage

. Flat or conical bottoms can be used.

. Sloping bottoms are more efficient in removing wastes.(rectangular)

. Adequate velocities are required to maintain self cleaning in flat bottom tanks.

. Flat screens are often used with the disadvantage of limited surface area and difficulty of cleaning

.mesh size should ensure that no fish can escape, though wastes must be allowed through. .

. The diameter of drain pipes should be large enough to facilitate quick drainage.

The Advantages of Tank Systems

Efficient use of space Efficient use of water Low maintenance Good self cleaning action Good visibility Flexibility of design Flexibility of application

Seasonal Tank Aquaculture

Tanks

Perennial

Stagnant, large aquatic resources

never dry out

Seasonal

Do not posses water through out the

year

Characteristics of seasonal tanks

• Cultivation is primary activity.

• Fishery is secondary activity

• Drying period: July – September

• Smaller and shallow

• Hold water during monsoon.

• Higher fertility of water

Uses of seasonal tanks

• Drinking

• Personal sanitation

• Agriculture

• Flowers

• Livestock and fisheries

Availability of seasonal tanks in Sri Lanka

•Area 100 000ha

•Dry zone

•Over 12 000 in number

Preparation of tank

• Remove rocks and tree stems

• Even the bottom of tank

• Let it dry completely

• Remove any carnivorous fish

• Repair outlets, inlets and spills

Suitable fish species - 01

1) Chinese Major Carp

• Big head carp (Aristichthys nobilis)

• Grass carp (Ctenopharyngodon idella)

• Silver carp (Hypophthalmichthys molitrix)

2)Chinese carp

• Common carp (Cyprinus carpio)

Suitable fish species - 02

1) Indian Major Carps

• Catla (Catla catla)

• Rohu (Labeo rohita)

2) Chinese carp

• Common carp (Cyprinus carpio)

Stocking ratios

C

Common carp bottom 2

Silver carp mid layer 2

Big head carp upper layerGrass carp 1:(3:1)

1-4m

CMC

CC

• Stocking density: 1fish/10m2

• Harvesting: partial

• Harvesting methods: gill and drag netting

• Marketing: sold to small and large scale vendors

Constraints

• Low survival of introduced fish by

Piscivorous birds

Carnivorous fish

• Introduction of fish without organizing the resource users lead to conflict among people.