algae?

I started using the forum this spring, and have had great success dealing with some situations that have come up! You guys are great. I now have something that I can't seem to get through. Last week we started having what I think is algae popping up on the floor of our pool. it is spotty all over.
Not really sure why?
Have a Taylor test kit, here are the last readings: Ph 7.8, FC 9 (high because I shocked it), CC .5, CYA 50ish. We have been sweeping every couple of days and I have shocked, but it just keeps showing up. I am following the directions I had in the spring to take care of the algae. We do fill with well water, and had to do so quite a bit this summer. I also have not had much luck getting my alkalinity lowered, last I checked it was 190.

What do the areas on the floor look like? Does it feel slimy? Could it just be dirt? In my pool, no matter how clean I think I get it when I vacuum (and I go VERY SLOWLY), once the water quiets down, I always have a little dirt that has been in suspension in the water while I vac and then re-settles on the floor.