Though it’s a common way to provide water, using this type of water source may lead to trampling of banks and contamination of water with fertilizer or manure, leading to an overgrowth of algae.
Limiting nutrients and light may discourage algal growth. For a new pond, consider placement that will minimize runoff of fertilizer and manure into the water. Use rooted aquatic plants and free-floating surface plants such as water lilies to compete for nutrients. Surface-floating netting can be used to shade the water.
Before using copper sulfate to treat pond algae, have the alkalinity tested. Strongly alkaline water will require more copper sulfate, but overtreating may kill fish and plants. Check with an agricultural extension agent for guidance in keeping algae growth under control.
To preserve soil around pond banks, consider fencing horses away from the pond and piping pond water to a tank outside the fence.