How To Construct Concrete Pond For CatFish Farming

Construction of concrete fish tank as an enclosure for fish housing could be built using a wide type of materials such as; metals, blocks, cement, gravels or stones and outlets and inlets facilities.

Factors considered before making choice of building a fish pond is;

(1) Durability
(2) Strength
(3) Impervious
(4) Permeability
(5) Workability
(6) Dimensional stability

Concrete mixture is a mixture of cement, fine (aggregate commonly called sharp sand), coarse aggregate and gravel (granite) mix together in appropriate proportion with water added to form a paste. Concrete could be plain or reinforced. Plain concrete is the one without steel rod. Reinforced concrete is the one embedded with steel rod. The steel rod technically called reinforcment bar. The choice either plain or reinforced is the function of specific use. A structure could be plain and reinforced.

Procedure For Concrete CatFish Tank Construction.

* Clear site of weeds/vegetation

* pegout required area

* remove the top soil until a firm lateric basement is reached at about 6.0m

* place frameworke in the perimetre of dug out area as desirable and fill with fresh concrete mixture of 1:3:6 cement/sand/gravel.

* Arrange coaches of blocks preferably in 4 or 5.

* insert the flush through pipe at base of tank.

* Plaster the interior.

* Poure water to the brim after two days and check for linkage.

* Treat the new pond two weeks before stocking.




Site Preparation

The place is cleared of ropes, cables and other items. Trees and bushes and other obstacles that hinder movement of heavy equipment around the site are to be removed - manually / animal power /using machinery. All vegetation including wood are to be cleared in the area (inclusive of 2 to 3 m beyond the dyke for workspace). Trees within 10 meters surrounding,  tree slumps, large stones, are also to be removed. The surface soil which has the highest concentration of roots and organic material is not suitable for pond construction. Hence, about 30 cm of surface soil has to be removed.


Construction Of Dyke

Dykes should be compact, solid and leak free. A desirable dyke is constructed using 15 - 30 percent of silt, 45 - 55 percent of sand and 30 - 35 percent of clay. A sufficient width of the berm (not less than 1 m) is required to stabilize slope. The embankment slope in horizontal to vertical should be 2:1 in good quality clay soil and 3:1 for loamy silt or sandy soils. To raise the dyke, the clay buddle (1:2 sand and clay) is deposited as 10 - 15 cm thick layer and it can be formed at centre or inside the waterside of the pond. The crest of the dyke should be sufficient to help allied farm activities and the top of embankment should be above 1 m. Extra outlet is essential on the embankment as a safety measure to avoid damage due to excess raise in the water level.


Digging The Pond And Construction Of Dyke

Types of pond

Specific kinds of ponds are required for specific life stage development of fishes - such as nursery, rearing, stocking, treatment  and broodstock pond. The rectangular pond is preferred than round shaped corners as it prevents the fish escape during harvest. An ideal length and breadth ratio of the pond is 3:1 is ideal, with breadth not more than 30 - 50 m. The total farm area can be divided as - nursery - 5 % of total farm area, rearing pond - 20 %, stocking pond - 70 %, and bio pond or treatment pond - 5 % of the total farm area.

Nursery pond - The size of the nursery pond is about 0.01 to 0.05 ha with a depth of  1.0 – 1.5 m. THE spawn (3 days old) are stocked in nursery pond, reared for a maximum of 30 days (to attain 2 – 3 cm length).

Rearing tank -  a tank where the fry are reared into fingerlings (to attain a size of 10 – 15 cm) and the culture duration is 2 – 3 months. The size of pond varies from 0.05 – 0.1 ha with water depth of 1.5 – 2.0 m.

Stocking pond - In stocking pond, the fingerlings (TL 10 – 15 cm) are reared into marketable size. The culture duration varies from 8 – 10 months. The stocking density varies according to the target fish production. The stocking pond is used as broodstock pond and breeding pond as per the requirement. However, the pond area ranges from 1 – 2 ha with a greater water depth of 2.5 – 3.0 m. There are no hard rules regarding the size of the ponds.

Bio pond or treatment ponds - these are large settling tanks, where the water used for fishponds is purified biologically. They may also be used as stocking pond. However, an even flat bottom is recommended for easy netting operation.
A productive farm should use its higher altitude area for construction of nursery pond followed by the rearing pond. The lowest area of the farm should be used to build the stocking pond, which will help in reducing the cost of construction and increase ease of farm management.


Pond Construction Types

The ponds are constructed by two types namely, dug out and embankment pond.

The dug out pond is constructed by digging the soil and is most    suitable to construct ponds in plain areas. It is to be scientifically,,, constructed maintaining shape, size, depth and other factors.

Embankment pond is more appropriate for hilly areas. Dykes may be erected on 1 or 2 sides based on need. This pond is economically viable but not ideal for fish culture because the size, shape and depth of pond cannot be fixed as per scientific fish culture specifications.


Inlet And Outlet Construction

Feeder canals are constructed to provide sufficient amount of quality water to the ponds except in ponds which are filled by rainwater. Inlets are provided at top of the pond and screens are used to filter the pumped water to avoid entry of unwanted particles to the culture system. The inlet pipe size has to be designed is such a way that it should not take more than 1 or 2 days to fill the pond.

The outlet pipe is set up at bottom of the pond. It is used to dewater the pond during harvest and partial draining for pond water exchange to maintain the water quality of the pond during the culture period. The outlet is constructed prior to pond dyke construction.


Soil And Vegetation Coverage Of Dyke

To reduce the soil erosion, creeping grass can be grown on the top and sides of dyke. The banana and coconut trees can be planted in the embankment. The slope of the embankment can be planted with grasses such as Hybrid Napier, gunny grass and elephant grass to supply feed to the grass carps reared in the ponds.


Pond Fencing

The ponds are fenced to protect from theft. Live fences also serve as windbreak, increase farm diversity, provide privacy to farm and improve the appearance of the fish farm. There are several ways to make fences. These include live fence, piled fence, woven fence, post and rail fence, wire fence, wire netting fence and stone wall. Each type of fence has its own advantages and disadvantages. Wired net fence is primarily used in fish farms to stop intruders and protect the fish stock.

References
Assiah, V.E., Ton, V.S. and Aidin, H., 1996. Small Scale Fresh water Fish Farming. Agrodok Series, (15).
Coche, A.G. Muir, J.F. Laughlin, T. (1996) Simple methods for aquaculture, management for freshwater fish culture, ponds and water practices. FAO, Rome (Italy).
Principle of aquaculture, online e-learning on Agricultural Education.
Pillay, T. V. R. and Kutty M. N. 2005. Aquaculture: Principles and Practices, 2nd Edition. Wiley-Blackwell.
Kövári, J. 1984. Inland Aquaculture Engineering. Aquaculture Development and Coordination Programme. Budapest, 6 June-3 September 1983. United Nations Development Programme, Food and Agriculture Organization of the United Nations, Rome. 1984.