The test kit isn't here yet, but I wanted to share a picture that clearly shows that FC 20 has made a positive impact. Beyond SLAM, I have a question about the algae. You can see from the picture that the algae is dead, and much of it has come off the wall. But what should I do about the remaining grey algae that just won't come off? Im brushing a few times a day, and it doesn't seem to want to come off. Even with the metal algae brush it won't budge. Any recommendation on stubborn dead algae removal from pool walls?