If you have algae in your pond it is probably not because you have put it there. A thick layer of string algae is not attractive and can certainly be detrimental to your pond life.
If you have algae in your pond it is probably because you have an excess of algal nutrients, including carbon dioxide in the water. Ponds without active aeration or gas exchange provide ideal growing conditions for this undesirable growth.
Persistent algae growth is often a symptom of an unbalanced pond ecosystem. You need beneficial bacteria in your pond to ensure that you maintain the correct level of nutrients in your pond. Without this balance you encourage its growth.
Pond Additives are specifically formulated to keep you pond healthy and maintain the balance in your pond. They can also remove unsightly and bad smelling sludge from your pond.
It is possible that your pond also has badly circulating or stagnant water. If you do not have sufficient aeration in your pond you can encourage the growth of algae. An air pump can dramatically increase circulation and aeration in your pond to help increase the dissolved oxygen in your pond and make conditions less favorable for pond life that prefers higher concentrations of carbon dioxide, stagnant or poorly circulated water.