As pools are opened for the spring, green water is not uncommon. At Isaacs Pools and Spas we receive numerous calls each day with customers saying: “My pool is green. What can I do about it”? Although we do all we can do to help customers over the phone, the only answer is that customers should take their water to a professional swimming pool company to have the water professionally analyzed. Green water can be caused by Algae blooms, malfunctioning filters or it could be more complicated, like a reaction between metals in the water and the oxidizers and sanitizers being used to treat the green water. The only way to know the difference is to do a full analysis of the water. You could be dosing the pool with high concentrations of calcium hypochlorite only to find the water getting worse. Some Algae, like Mustard Algae, requires a special Algaecide to kill it. Shocking alone will not eradicate it. In other cases customers make the mistake of self-diagnosing the Mustard Algae and continue to dose the pool with Algaecide for Mustard Algae, not realizing the metal in the Algaecide used to great Mustard Algae is raising the level of metals in the water and potentially causing other problems. Another common problem that causes green water is when leaves and other debris are on the bottom of the pool. In this case, the water can test perfect, but the water still be green. In short, if you have a green pool, take a water sample to an experienced and professional pool company for analysis. A professional water analysis and some question and answer with your local pool professional will reveal the cause of the green water. Only then can the answer to “My pool is green. What can I do about it” be answered.