Move the fountain to a location that does not receive full sun. Sunlight can warm the water inside the fountain, which will promote the growth of algae.
Clean the fountain thoroughly using a disinfectant solution. Mix10 percent bleach with 90 percent water to create a common cleaning solution for this process.
Fill the fountain with distilled water. Distilled water has impurities removed from the water through extensive boiling and condensing steam from the boiling process in a clean container. Fewer impurities will not allow algae to grow in the fountain.
Add a water purifier to the fountain. Most hardware or gardening stores will sell a simple solution you can add to water that will prevent algae growth in the fountain.