I just came home from 3 weeks away. When I left pool was clean , clear good chlorine number and PH balanced. After vacuuming ...I noticed lots of black spots scattered all over the bottom of my pool. Brushing in the usual manner did not remove them. My test results are as follows
We had two days of drenching rain while I was away ( over 5 inches of rain)
Immediately added bleach to raise my chlorine to the high side of normal for my CYA.
My concern is black algae....I read the page on how to treat it and scrubbed like crazy this morning on all the spots I can reach...the ones in the center I can't reach ...I'm going to follow the suggested steps for the next 3 days but then I have to travel for work again.
What other steps should I take and in what order should I try and get my other chemicals back up to proper levels.
I have already raised chlorine ....added acid to adjust PH and put in salt . I also noticed my SWG was set at a much lower percentage than I usually keep it....which may have contributed to the much lower chlorine levels..along with the dilution of salt due to rain.
Ps- I also noticed a whole lot of gravel from my roof all over the pool deck ...my roof is needing to be replaced soon and I'm constantly cleaning up the stones and vacuuming them from pool...could this be the cause of the spots? Since they sat on bottom for a long time? Anyway to confirm Black Algae?