Does HP kill string algae?

There are hundreds of different kinds of string algae. I've had at least 2 kinds in my pond and HP killed both kinds. Some people on the web have said it didn't work for them although few details are ever given. Dumping some HP directly on some string algae should tell the story. It should turn gray or white within hours or at least within a day. Some times it seems to disappear completely but that's not normally the case. It does not work on green water. I have no idea why not. Maybe it does on some kinds of unicell algae or maybe at higher doses. But from my experience it had no effect.  more