In some Lime Green cases, pond owners have tried to fight the green, but it doesn’t go away. Limestone, is recognized as a cause for a spike in your pH level. So if you have any limestone in or around your pond that could be a problem and we suggest you get it away from your pond and treat the pH. Some folks have to drain the pond completely, then add fresh water. If this is the case, make sure you de-chlorinate the water. If it’s gotten to the point where you need an outside solution, we would suggest an Ultra Violet Light! We at Backyard Blessings provide submersible UV lights that can be installed under water or outside your pond. The UV light will control the single cell organisms that will turn your pond lime green.