BLACK SPOTS

[DEBBIE9]

I HAVE BLACK SPOTS OR BLOTCHES ON THE BOTTOM OF MY PEBBLE CRETE POOL
I HAVE LOTS OF TREES HANGING NEARBY & SOME CUDAGI TREES WITH BLACK SOOT WHICH FALLS ON EVERYTHING BUT THIS WASHES OFF VERY EASILY WITH SOAPY WATER
THE SPOTS ON THE BOTTOM DONT EVEN SCRATCH OFF WITH THE HARD BRUSH
THE POOL IS BALANCED & I HAVE TRIED ALGAECIDES
THE SPOTS ARE SPREADING FURTHER ALL THE TIME

CAN SOMEONE PLEASE HELP?

[Poolz]

Hi Debbie
Why have you assumed the problem is algae? It could be a metal stain of sorts - most likely manganese or silver.

Have you tried the sock test? Apply a sock filled with chlorine to a stain for 10 - 15 minutes. Check if the spot changes. If so it's an organic problem and probably algae.
Then apply a sock filled with dry acid to a stain for 10 - 15 minutes. Check if the spot changes. If so it's an inorganic problem and probably a metal stain.

P.S. PLEASE DON'T SHOUT HERE (we can all hear perfectly)