The catch of adult C. idella from fishponds has remained low. Because they are unable to adapt to the environment in fishponds, the fish easily become ill. In ricefields, on the other hand, the ecological environment is suitable for C. idella , and few, if any, become ill. This is why the output of freshwater fish can be doubled. In this method, the raising of C. idella or tilapia in ricefields is organically combined with the growing of azolla.
Rice is grown in the field, azolla on the surface of the water, and fish in the water.
Fish feed on the azolla, and the field is fertilized by fish excrement. Melons and beans can also be planted on the banks of the field to form a vertical cultivation system. Instead of the conventional equal-distance planting method, rice growers use wide and narrow rows. They raise azolla and fish in the wide rows and plant rice in the narrow rows. This keeps the field well ventilated and maximizes the use of sunshine and the effects of edge rows.