Keeping Pond Stones From Turning Green

That green you see is algae. It's necessary in your pond, any pond that is in good condition will have it. It's the natural flow of things. It's probably the reason your water is clear. Any flat surface in your pond should be covered with 1-2 inches of small rocks. That prevents dirt/debris from being stirred up from the bottom. If you don't want the green, then you want a swimming pool. If the water is clear that is great. I have never seen any pond or water feature without any green. I say just let it be.