Third summer with the pool. A few strange issues this year (missing tiles, thrips, strange stains, algae?). I'll be posting in other topics, but want to get suggestions on the attached pictures. First set is obviously alage, but below the waterline, cleaned off easily and hasn't shown up anywhere else. The second set is in the deep end, does not brush off at all, had shown up shortly after I opened (I did the AA treatment at opening, late April), disappeared and then reappeared over the weekend. I noticed 2 or 3 spots Sunday evening and then today a bunch more (10 - 20) have shown up.
CYA: 50 (2 weeks ago)
OCLT last night 0.5, maybe 1.0 (3.0 -> 2.5 or 2.0); pH had crept up slightly to 7.4.
Water was clear when I first saw the algae, but has gotten cloudy the last day or two. I added extra liquid chlorine and MA tonight and will check clarity tomorrow. I have not had to go through the full shock process in the previous two summers and the water has remained clear and beautiful (most of the time).
My questions. Is the green algae 'mustard' algae and do I need to keep a close eye on those spots and look for other spots? What are the black spots? Best way to deal with them?
I did the AA treatment for metal stains when I opened the pool at the end of April. When I opened, the pH was above 8.4 and I think I have a calcium scaling issue (that is for another post). I've been hesitant to let the FC or pH get too high because of that. I have been adding sequestrant every week or so since April.