Preparation and maintenance of a pond for carp farming in Sri Lanka

For natural
aeration of pond water, the pond should be oriented east to west. The length to
width ratio of the pond should be 2: 1 and the depth of the pond should be 1.5
m. The pond wall should be 3 m wide.
In order to
prepare a pond, eradication is required. There are two types of eradication: physical eradication and chemical eradication. Physical eradication is achieved
by Sun drying for 2-3 weeks until the formation of soil cracks.
Bleaching powder
(25g/m2) is used to do chemical eradication. The pond bottom should
be thoroughly wetted before bleaching and then bleach for 1-3 days. Then fill
the pond to 12 inches with water and after 2 days, water should be released to
minimize the bleaching powder toxicity, and water should be filled to 48 inches
level again. As another chemical eradication method, can use bleaching powder
with urea (1g/m2 urea and after 24 hrs 12g/m2 bleaching
powder). The ponds should be free from aquatic feeds, wild fish, and predators.
Ammonia 25g/m2 is sometimes used to kill wild fish like stinging
catfish. Lime (50 g/m2) is a good pesticide to use.
Fertilization
has a bigger role in semi-intensive carp farming. Fertilizers might be
inorganic or organic. Organic fertilizer consists of fresh cow manure, poultry
manure, green leaves, and compost. For early fertilizing of ponds to grow
planktons, cow dung (750g/m2) or poultry manure (250g/m2)
could be used. Auxin and cytokinin hormones are found in fresh cow dung and are
beneficial to phytoplankton growth. Use 1g of TSP (powder form) and 3g of urea
per m2 in combination with organic fertilizers for quick results.
Weekly manuring is advised if necessary. Before applying fertilizer water level
in the pond should be 1.5m and then the water level in the tank should be
gradually raised.
After two weeks
there is a significant change in color of the pond water (immediately dark
brown and then yellow after that green), and after two weeks, excellent culture ponds can be obtained by this method. The visibility of the Secchi
disk should be between 25 and 30 cm. Plankton density must be 20-25cm in brood
and brood ponds and 45cm in brooders ponds. The pH of the medium can be
adjusted by adding lime. Eichhornia sp. can also grow in corner of the ponds to
absorb excess ammonia produced by excess feed, however, as Eichhornia sp. is an
invasive alien species, that should be planted in small quantities.