Question: asked about the reason for death of fishes and disease occurence
Answer: told him to the following methods
1. water exchange of pond after that liming.
2. agri-lime - 10kg/bigha or dolomite at 9am - 25kg per bigha.
3. disease - mix potassium permanganate  in water for at 2mg per litre and apply it by splitting in the pond.
4. or tie some paddy straw and place it on the surface of the pond. make many such bundles and place it on each corner of the pond.