After large rains and a poop in swim diaper incident, shocked pool. Two days later, black spots. FC 6 Alk 130 CH 230 Ph 7.8 cya 20. Saltwater generator. Water temp 88f. They vacuum (to waste) right up. I can poof them up and net thousands of short black debris. Added stabilizer and performed overnight chlorine test (pump off overnight) and passed - pool had no black in morning. Pump ran as usual during day, and small group of black appeared. Levels same as day before except FC dropped to 4. I can’t find much regarding black algae and fiberglass. Could it be black algae if not stuck to the surface?
Black algae in fiberglass pool?
- Thread starter Beth33
- Start date
- Jul 21, 2013
- 53,923
- Pool Size
- 35000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
Not likely black algae.
Capture some and rub it on a white paper towel. What does it look like?
Capture some and rub it on a white paper towel. What does it look like?
- Jun 22, 2014
- 48,147
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
Just to clarify, the pump doesn't need to be off. In fact, I would recommend it remain on (low is fine) for the OCLT. But if you do turn it off, you have to ensure the pump is running for at least 30 min before taking the morning water sample for the second FC test. I am also suspicious about it being black algae, especially since it can't dig its roots into the gelcoat like it would a plaster surface. Have any other items been blown into the pool lately perhaps? Landscaping work, mowing, etc?
It looks like short black straight hairs. To clarify, I meant the SWG was off. Not the pump. It’s running 24/7.