It slowly started earlier in the summer when the wife and I went on vacation for a week and used cal-hypo in a floater to maintain the pool. When we got home, the cal-hypo was completely gone and the pool was still blue, but there was signs of algae growth on the flat parts of the steps. I brushed it with a nylon brush and put some bleach directly in that area and it went away pretty much.
The following month we had to leave town for a couple of weeks for a family emergency and there was no way to maintain the pool while away, so I put the normal cal-hypo floater in and prayed it wouldn't be too far gone when we returned.
Came home to a pool that was quite green, but came back in <24 hours with 6 gal bleach. Except, in the shallow end (the steps and a corner that gets lots of sun) there was black algae. I attempted to keep this one at bay the same fashion but it seems to be spreading. I am now pouring about 2 gal bleach in every 6 hours and brushing with a steel brush and its not reseeding. I stole a tri-chlor tablet from my brother and let it sit on the stairs where the algae was and ate it up, meaning I have black algae (?).
I have since dropped that tablet into the shallow end where the algae is most prevalent and go out and push it around with the pool brush every 30-45 min, and it seems to be eating away at the algae, but only at small chunks. I am almost to the point where I want to go buy a bucket of tri-chlor and drop the tablets all over the shallow and let them have at it, but I was wondering if granular dichlor would do just as well there?
what is the easiest and most cost efficient way to get rid of black algae? would it help if I covered that area of the pool with a tarp so the sun doesn't eat up as much chlorine? how much would it hurt to put granular chlorine across the shallow end where the algae is and let it sit for 2-4 hours and brush it away?