The Setup:
SWG Gunite pool, plaster is 13yrs old, well cared for. But some areas of degrading tile grout esp around skimmers.
Typical reading before SLAM (I kept it pretty consistent):
FC 5
CC 0
pH 7.7
TA 70
ch 400
CYA 80
Salt 3000
Daily sweeping/skimming. I do 100% of the maintenance and use the Fas-dpd test kit
The Story
2 years ago the pool started having pinheads of black algae. Never bigger than a pencil eraser. Mostly in the shady part of the pool though some in brighter areas, and especially around the skimmers where the tile grout is in poor condition. we made frequent trips to Texas beaches and I suspect we brought it back from the ocean with us. It always passed the OCLT. Picture is not my pool and mine had fewer dots, but looked similar.
Last summer the dots started multiplying faster….
February 2018 I bit the bullet and SLAMed it using liquid chlorine to 100ppm (!) for 20(!) days. I tried hard to kill this stuff. Also poured granulated shock directly onto as much of the mold spots as possible. Disposed all the pool toys, tools, towels, bathing suits, etc. Swept with SS brush 2xday for 2 weeks. It took a solid week for the dots to disappear. Let the CL level creep down and have maintained it at 10ppm since.
The Problem
Last week – noticed the return of a few tiny dots in various areas of the pool. GRRR!!! Yes it is black algae, it scrapes/smears with a fingernail, and WILL NOT DIE!
So now what? pool passes OCLT. Numbers are stable. Help, you are my last hope.
SWG Gunite pool, plaster is 13yrs old, well cared for. But some areas of degrading tile grout esp around skimmers.
Typical reading before SLAM (I kept it pretty consistent):
FC 5
CC 0
pH 7.7
TA 70
ch 400
CYA 80
Salt 3000
Daily sweeping/skimming. I do 100% of the maintenance and use the Fas-dpd test kit
The Story
2 years ago the pool started having pinheads of black algae. Never bigger than a pencil eraser. Mostly in the shady part of the pool though some in brighter areas, and especially around the skimmers where the tile grout is in poor condition. we made frequent trips to Texas beaches and I suspect we brought it back from the ocean with us. It always passed the OCLT. Picture is not my pool and mine had fewer dots, but looked similar.
Last summer the dots started multiplying faster….
February 2018 I bit the bullet and SLAMed it using liquid chlorine to 100ppm (!) for 20(!) days. I tried hard to kill this stuff. Also poured granulated shock directly onto as much of the mold spots as possible. Disposed all the pool toys, tools, towels, bathing suits, etc. Swept with SS brush 2xday for 2 weeks. It took a solid week for the dots to disappear. Let the CL level creep down and have maintained it at 10ppm since.
The Problem
Last week – noticed the return of a few tiny dots in various areas of the pool. GRRR!!! Yes it is black algae, it scrapes/smears with a fingernail, and WILL NOT DIE!
So now what? pool passes OCLT. Numbers are stable. Help, you are my last hope.
