Hi Ann, Welcome to ATP!
I don't have a pond and don't know a thing about them but I'd be wary of adding vinegar to the pond without knowing the proper amount for the quantity of water. If you have fancy Koi and other fish you sure don't want to harm or kill them in the process of trying to control algae. Hopefully someone more knowledgeable about backyard ponds will be along with some advice for you soon. Meanwhile, I googled and found this information regarding pond algae control that might be of help:
http://www.drsfostersmith.com/...
Again,
Lin
