Duncan,
Sounds like I was wrong about the algaecide. (Not the first time.)
You can rake out a lot of the algae, but you must dispose of it somewhere such that the nutrients from the decaying algae DO NOT run back into your pond.
If that doesn't work, or work well, then it might be worth your money to have a licensed applicator do your pond. Since you don't have any stocked fish, he should be able to treat heavily and get control in a single application. (Hopefully!)
