I believe I have 2 small spots of black algae growing in my spa...started with one spot in the corner that was fairly small, but now it's a little bigger and there is a new spot near it up on the wall.
Our spa spills into the pool and the water recycles between the pool and the spa.....we do not keep the spa heated so it stays at the same temp as the pool year round as it only takes about 10 min to heat it up when we want to use it and that's not very often to be honest. My test #'s are perfect for where I want to keep them...considering I'm running a slightly neg CSI to place a band aid on my high CH level....I'm passing OCLT's with ease....but the spots remain and won't brush off. The water in both pool and spa is crystal clear and there are zero signs of any algae in the pool itself or any of the tile or coping.
Do you think I'm right about it being black algae? And if so, does that mean I have to start the shocking process for the entire pool????? How I dread having to do that!! I just recently got everything in check for hitting my target CSI.
FC - 8
CC - 0.5
TC - 8.5
pH - 7.4
TA - 70 (we run lots of water features frequently)
CYA - 60 (we have 100% direct sun exp all day)
CH - 550
Any advice is appreciated!