Question: asking about the prevention of ulcer disease of fish
Answer: told him that this kind of disease occurs by bacteria and it is necessary to maintain a good water quality to prevent this kind of disease and its also necessary to apply agricultural lime @ 20kg/bigha monthly and potash @ 350gm/bigha to maintain a good quality water where fish can grow well. 
and if these kind of disease occurs in near future than apply @ 150ml cifax in per bigha pond water.