Health When swimming pools are covered with algae, it’s important to treat them immediately. Algae not only discolors the water, but it can also invite harmful bacteria into your pool. These bacteria can cause a number of health concerns for swimmers, including a skin rash, various bacterial infections of the ears or eyes, and respiratory issues. They can even lead to a fever or diarrhea if ingested accidentally. Toxic algae blooms are becoming a concern in many parts of the United States, especially around the coasts. These blooms can be dangerous for swimmers, wildlife, and local economies. Typically, a combination of unbalanced chemical levels (low chlorine), warm temperatures, stagnant water or clogged filters gives algae spores the perfect conditions for growth. When the right conditions occur, algae spores can grow into a bloom within hours.