Freshwater aquaculture

Unit 3 - Nursery, Rearing and grow-out ponds

3.3.3. Supplementary fertilization
Ponds are fertilized prior to stocking fish with manures and fertilizers, when they are applied as a basal dose. Due to overfeeding by fish on the plankton and other natural fish food organisms, the plankton biomass may get depleted. In order to maintain the crop of fish food organisms, supplementary feed post-stocking may be required. When the water starts to lose its plankton turbidity, amounts less than basal dose of fertilizers need to be applied to ponds and fortnightly intervals. For example in carp rearing and grow-out ponds are manured with cow dung as a basal dose of 3-4 tons/ha. The ponds are subsequently fertilized with cow dung at a dose of 0.5 tons/ha at fortnightly intervals. However, supplementary fertilization should be followed with caution since application of excess of fertilizers and manures may lead to poor water quality of the pond, or undesirable blue green algae such as Microcystis may develop which apart from being toxic, will not form food for the fish