It can be a challenge to keep pond water clear. The location of your pond is one big factor. Tree leaves can cause lots of trouble and so can hot sun, which makes algae spread like crazy. Keeping your pond clear of debris, with the right strength of recirculating pump is good preventative care. Barley straw is shown to do a good job slowing down or preventing the growth of algae as well. If you have too many fish for the volume of water, their waste can also dirty a pond. More is not more with fish! If your water is getting murky, often from algae dispersed throughout the pond, you can try my water filtering trick.