I have a Dolphin M400. I’ve run it everyday the last few days, if not once, twice. But it still seems there is always the dead algae in the same place on the floor and steps by a return line. Is the filter not filtering it out?
The water is blue and clear. But just a few spots of the dead algae. And then in the deep end when I brush an angled wall it kicks up the “dust”. So do I still have active algae?
So a couple of things I just noticed. I think you said your new CYA level is 50, if that is the case then your SLAM level is 20 for FC. If you keep you FC lower than that the SLAM will take longer. The more often you adjust your FC to 20 the less time the SLAM will take.
Also when running your M400 make sure you are using the fine pleated filters. That will help you clean our the deal algae.
If you can test in the rain (no lightning) then you can keep testing and adding. Rain won't really affect much. Even if it gets high enough you have to drain some off it's going to be pretty minimal compared to the total pool volume.