Fish manure also enriched the field. In this way, costs were reduced while net profit was increased. Conclusion Experiments in 1987 indicated that the high-yield rice azolla fish system was a success. Fish yields and net profit were increased and rice yields were maintained. Grass carp quickly grow to a large size.
Silver carps are smaller and have a lower commercial value.
The appropriate proportion of silver carp to grass carp must be studied. Bream grow slowly and should be raised in small proportions in rice fish azolla fields. In 1987, dikes and fish nets were used to prevent the fish from eating rice. This was expensive in both capital and labour. Many late rice seedlings were eaten by the fish in 1987, which resulted in a decrease in rice yield.