Mixed fish farming system in Bangladesh.

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Cultivation of Rui, Katla, Mrigel, Rajputi, Nilotica, Silver Carp etc. is profitable. If these are cultivated in a scientific way, the risk is less and the cost is less. Therefore, there is no possibility of loss if the fish is mixed in a scientific way.

1. Pond selection: The success of fish farming largely depends on pond selection and pond preparation and management. There is water throughout the year or seasonal ponds can be cultivated in these two types of ponds. It is better if the size of the pond is between 1-3 bighas. However, fish can be farmed in ponds larger or smaller than this. The pond should be weed free and open and flood free. The depth of the pond should be 3-5 feet. Ponds that have water for 5-6 months in a year should be selected. It is better not to have such large trees on the banks of the pond and the leaves of the trees can fall into the water. If the shade of the tree falls on the pond, the natural food of the fish in the pond cannot grow in large quantities. In addition, the leaves of the tree rot in the water, destroying the normal quality of water and reducing productivity. Generally, loamy and muddy loamy soils are best for ponds. The pond should be rectangular for fish farming management. In the interest of overall management, the location of the pond should be close to the homestead.

1. Pond preparation: The pond must be well prepared before stocking the fry in the pond. In the interest of physical growth of fish, it is necessary to ensure that the required amount of natural food is produced in the pond. The various stages in the preparation of the pond are- control of aquatic weeds, control of giant fish and unwanted animals, application of lime and fertilizer etc.

Aquatic weed control: In the presence of unnecessary weeds in the pond, fish farming is hampered in various ways. Disrupts the movement of fish and provides opportunities for fish-eating animals to hunt. Aquatic weeds make soil and water infertile by absorbing soil, water elements or nutrients. Fields, especially water, are deficient in oxygen. Aquatic weeds absorb most of the water nutrients created by the application of different types of fertilizers. As a result, the required amount of fish food is not grown in the pond. Therefore, algae, floating, creeping and submerged aquatic weeds should not be allowed to grow in the pond. Aquatic weeds usually include water hyacinth, kalmilata, helencha, zhao, etc .; Which must be controlled. Sunlight helps in making food in the pond water and weeds prevent sun rays from entering the pond water. Therefore, it is essential to control all types of aquatic weeds with roots. If fibrous algae is present in the pond, it can be controlled by using mulberry in moderation (8 g per cent). Other weeds should be cut and pulled from the pond.

Removal of giant fish and harmful animals: By drying the pond, giant fish such as boal, chital, shoal, carrot, ayr, taki etc. and unnecessary fish such as mala, chanda, chela, putti, darkina etc. should be removed completely. Measures should be taken to kill other animals harmful to fish such as snakes, frogs, crabs etc. Pond drying should be done in the dry season. After drainage, the soil at the bottom of the pond should be dried in the sun for at least seven days. Even after this, if there is excess mud, then some mud has to be removed. Then after drying the soil, at least 2/3 days after cultivating the bottom of the pond, the required amount of water should be provided (if possible) or wait for rain water.

If it is not possible to dry the pond for any reason, giant and unwanted fish and harmful animals should be suppressed by pulling nets or applying poison.

1. Lime application: Lime application is essential to decontaminate soil and water in ponds, to destroy fish disease germs and parasites, to increase immunity and calcium in water and to increase the productivity of ponds. The exact amount of lime depends on the soil and water quality of the pond. Usually when the bottom of the pond is dry, lime powder should be sprinkled all over the pond at the rate of 1 kg per cent. However, if the acidity is 4 then 10 kg, if 4.5 then 5 kg, if 5.5 then 3 kg, if 7.5 then 2 kg per cent has to be applied. Water should be supplied to the pond 2-3 days after lime application. If the water is not dried, lime should be mixed with water at the same rate in the pond filled with water and sprinkled all over the pond along the slope.

1. Fertilizer application: Organic and inorganic fertilizers should be applied in the pond to grow plant and animal natural food or plankton for fish in the pond. Fertilizer can be applied at the following rate at least 4-5 days after lime application:
2. Poisoning test: If there is poisoning in the water, the fry will die and the exact result will not be available. Water poisoning should be checked before releasing the fry. In this case, if you leave the fry in any container or leave some fry in the pond water for at least 24 hours, you have to take measures to release the fry if it does not die. The day before the release of the fry, the horara or net can be pulled 2-3 times in the pond.