However, it should be noted that fish farming must avoid direct sunlight, because under direct sunlight, algae multiply in large numbers, the water body is eutrophic, the dissolved oxygen in the fish tank is reduced, and aquatic plants in the fish tank will die because of too strong sunlight. There must be a filtration system in fish farming, because excrement and leftovers will be produced continuously in the process of fish farming. If there is no filtration system, the water quality will become very poor, leading to eutrophication.