Although hippopotamus will wag its tail constantly when defecating, and the feces will be scattered all over the floor, after a large amount, the feces will sink to the bottom one after another, forming a large area of water and feces deposition. These feces need a lot of microorganisms to decompose, and microorganisms will consume a lot of oxygen in the water when they decompose. At the same time, the fresh manure itself contains some harmful substances, and the harmful substances produced by microbial decomposition of manure make it impossible for fish to survive in the river section with dense hippos.

More than 4,000 hippopotamus droppings are a disaster for some fish in the Mara River, but as we said at the beginning, animal droppings are a natural fertilizer, and hippopotamus droppings are no exception. According to the researchers' analysis of hippopotamus feces in Mala River, they are one of the main nutritional sources of aquatic plants and algae in Mala River. Usually, some undeposited feces will drift with the water and be decomposed by microorganisms, becoming nutrients for aquatic plants and algae.

At the same time, the decomposed feces will also be directly used by fish and other aquatic animals. Because there is more feces in the water and the water is more fat, aquatic animals, especially fish, grow and reproduce faster, and the death of fish caused by hippopotamus feces is less than that of fish after nutrition supplementation.