Black splotches on bottom of pool

[Emarshbuck]

this happened a few months ago and it went away after I slammed. currently slamming again (4 days) and I don't see any improvement.

cya = 40
TA =170
water temp is 84

I'm keeping FC @ 16.

I don't want to use my wire brush except as a last resort....is this considered black algae?

suggestions?

thanks

ed

 

[zea3]

Try scrubbing the spots with a chlorine puck to see if the stain lightens, or see if you can scrape some off onto your fingernail and rub it on plain white paper. If it makes a dark green smear it is black algae.

 

[Emarshbuck]

and if it is, what do I do?

thx