Answer: Most ponds will show naturally discoloration for several weeks in the spring as the water warms up. Once the water temperature stabilizes and the plants begin to grow more actively and the surface is covered by waterlilies, the algae naturally subsides.
Summer algae problems are usually related to excess fertility in the water (overstock of fish, overfeeding fish, overfertilizing plants) and to excess sun penetrating the water (lack of surface plants) and to lack of underwater plants to filter the water and use up excess nutrients. Correcting those conditions should control algae to an acceptable level.
Keep in mind also that surprisingly the water in a healthy pond is not crystal clear; it is clear enough to be able to see your hand about a foot deep. In the meantime if you wish you can float some barley straw in the pond, it helps control some kinds of algae. Keeping the water aerated can help with some kinds of algae. And, you can certainly skim off any of the algae that rises to the surface or use a stick to wind up and pull out the stringy type of algae.
Finally, netting the pond in the fall to prevent leaves getting in it and cleaning up plant debris after frost can also help reduce algae the following season. I hope this helps.
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