When is phosphorus bad for the environment? Phosphorus is one of the six most used chemicals in nature, so it's not all bad. But when too much phosphorus gets into a body of water, it can stimulate the growth of algae -- so much that the algae cover the water in a sheet that blocks out sunlight. Plants can't grow under this "red tide" of algae, so they die. Bacteria eat the plants, and use up all the oxygen in the water. That's bad news for the fish, shrimp and crabs, or anything else that lives in the water. Red tides aren't always red, they can be green, too. Too much nitrogen can also cause a sheet of algae to grow out of control. Phosphorus and nitrogen are common ingredients in fertilizers as well as feed.