Legal analysis: illegal. If you build a fish pond on the contracted land of your home, the village Committee with basically no formalities will agree to have a contract, but it cannot be basic farmland.

Legal basis: Article 37 of the Land Administration Law of the People's Republic of China. Non-agricultural construction must economize on the use of land. Those who can use wasteland shall not occupy cultivated land; Those who can use inferior land shall not occupy good land. It is forbidden to occupy cultivated land to build kilns and graves, or to build houses, dig sand, quarry, mine or borrow soil on cultivated land without authorization. It is forbidden to occupy permanent basic farmland to develop forestry and fruit industry and dig ponds to raise fish.