Black algae or rusting metal chip?
In a previous post I mentioned that I think I have a small metal chip in my paster that is rusting. Its very small - smaller than a pea, but left for a day, it grows to about double its size. When brushed, it looks like rust and plumes of rust can be seen coming off, and then its back down to its small size.
Using a tube I put muratic acid on it which just made it turn rust colored until I brushed it and it is back to a blackish color.
I caled the PB and he is saying its black algae (although he has not come out to look) and so I just need to shock the pool.
CYA = 80
CH = 7, but did go down to 5 one day while my SWG was being fixed.
Ph = 7.6
All other numbers are within range.
One other note - I did add extra salt by mistake and am at 4700 instead of 3500 and that is about when this stain appeared (out of nowhere).
How can I check to see if it is algae or not? If it is black algae, and I scrubbed it with a chlorine tablet, would it go away?