I started composite carp culture in 2015 on one acre in Bharatpur. Catla, rohu, mrigal. First two years I lost money. The reason was stocking density. I put in far too many fingerlings because I thought more fish meant more money. They grew slowly and half of them died when the oxygen dropped in May. Now I stock around 5,000 fingerlings per acre, not 9,000. Production is better with fewer fish. I also keep an aerator running at night from April to June, which alone stopped the summer mortality. The money is decent but it is not passive. Pond preparation, liming, checking water every single morning.