英语翻译The not required and recovered nutritious substances the

英语翻译
The not required and recovered nutritious substances the fish will discharge.I.e.,constantly new nutritious substances will flow in the pond by the inflow or will entry our water from the air and in addition Fishes by their excrements will add more nutritious substances into the water.
这篇文章主要将水中营养物质过多造成水质污染,这段话前面主要是写了鱼类的食物链.