Certain points should be kept in mind while constructing the fish ponds. Enumeration of these points together will help the fish farmer to plan the construction of the pond in advance and to avoid future problems. It also will help him to have more accurate financial estimates and plan for his fish rearing enterprise. The key points are the following.
1. Pond Size
There should be proper size and shape for ponds used for various poses like breeding, spawning, hatching, nursery, rearing and stocking. Often ordinary people have only one pond in which they rear fish from the nursery stage to the selling stage. Under such conditions they should have at least a pond size of 70 ft long, 35 ft width and 4-5 ft water depth. The ratio between the length and width of the pond should be maintained between 2:1 to 4:1 (the width should be less than half the length). This is to provide the fish long stretches of swimming and feeding space and also for easy netting. Otherwise the optimum sizes of the ponds for various commercial purposes are the following. The size of various ponds are given in relation to pond of one hectare of stocking pond.
2. The sides
The sides of the pond should be made really firm and non collapsible. This is done by various ways like giving proper slope, compacting the soil, building or lining the sides with bricks or stones or concreting etc. A collapsed pond is like a broken vessel which cannot hold water in it.
3. Water retention
The pond should retain sufficient water throughout/the rearing and growing season. In other words it should be made leak proof. This can be made by compacting the soil, puddling the soil, adding more clay and other binding material to soil at the bottom and at the sides of the pond. The top soil layer (up to 6-9 inches depth) should be so compacted that practically no seepage loss is there, though compacting is a one time labourious process.
There should be proper drainage facility. We should fix a proper outlet from the pond through which we should be able to drain the pond fully or partially at any time without allowing the fish to come out.
The inlet brings in water into the pond. This should be constructed in such a way that silt, leaves or other plant parts should not come into the pond. The inlet should also control the quantity of water coming into the pond whether during flood, rain or dry season. In short, inlet controls the quality and quantity of water coming into the pond.
The outlet could be same as drainage or separate. In a running water pond a separate and permanent outlet is fixed besides a drain. The outlet is fixed in such a way that the fishes from the pond should not escape. The water level in the pond is maintained and the quantity of water flow can be controlled.
Proper bunds of about 2-2.5 ft. height and of convenient width is needed all around each pond. These bunds serve not only as boundaries but also as passages to move around and between ponds. The dimensions of the bunds such as length, width at the bottom and top, the height and thickness of the bunds should be even and uniform through out the bunds. Similarly the compactness of the bunds also should be uniform.
Proper approaches to the pond site, to each pond and to the bottom of each pond is necessary for easy movement of people and things in the fish pond area.
= Siltation control
There should be proper control of the silt possibly coming into the pond during the rainy season. There should be properly constructed silt catching traps before the water enters the inlet.
= Quality of water
The quality of the water should be maintained suitable for the fish growth, especially the amount of dissolved oxygen content. The water also should not be acidic or alkaline but neutral for all the fresh water fishes. But for the brackish water fishes one should ensure the brackish water. Sometimes the water may be acidic or alkaline at the source itself due to the type of soil and the rocks through which the water comes in. The water also should be clean and transparent to allow sunlight to reach the bottom of the pond.
= Natural feed production
Natural feed consisting of aquatic flora and fauna are essential for healthy fish culture. Hence in all the fish ponds special care should be provided to generate maximum natural feed.
= Technical know-how
In actual situations of fish rearing what is mostly lacking is technical know-how. Proper technical knowledge backed by sufficient theoretical understanding is the brain and back bone of fisheries. For long term fish culture, timely updating of the technical know-how is necessary for the success of the enterprises.