Filamentous algae. Normal for a new pond until some macrophytes get started. It's using nutrients i.e. phosphorus, nitrates, in the water. As long as it doesn't take over your pond I wouldn't worry.
Try to get some kind of buffer strip of vegetation around the pond to keep it at bay.
Oh and aquatic vegetation? If you build it they will come. Hopefully not the wrong kind!
Last edited by Cecil Baird1; 03/22/14 06:31 PM.