I'm in the process of treating a black algae infestation. I've been lax and lucky for the previous 6 summers but lost this year to black algae and am now a convert to TFP methods and test kits. Thank you for being here. I've read everything I can on this site about black algae and think I understand the principles but am not sure how much effort or whether I want to put more effort into this old pool that came with the house. I need some feedback from some experts. Rainwater harvesting in my pool is starting to look appealing. Maybe a Koi pond? I would really like a "natural swimming pool" - 1/2 for human and 1/2 Koi pond.
OK - latest tests in 1/2 the pool volume (estimate 7500 gal of 15,000 gal)
The black algae is covering a lot of the bottom, there are some rough areas in the plaster where the algae has taken up residence plus the blue-green spots on other areas of the pool. The rough areas are from some ignorant person, who shall remain nameless, putting trichlor pucks in the pool during the winter for passive chlorination. Well that wasn't good for the plaster but it appears still intact.
I drained the pool to about half with the idea that I will be diluting the CYA, I find it easier to scrub entire pool bottom, and I need less bleach. However, mixing chemicals is an issue somewhat since I can't use filtration until I fill the pool. I'm finding scrubbing the pool bottom with the 4 inch stainless brush and the foot long stainless brush on a pole very difficult and inefficient. When the FC was lower I felt more comfortable scrubbing the plaster up close, with the 4 inch stainless brush in my hand, wearing snorkeling gear and weights.
I notice that the black algae is fading as the bleach and scrubbing is working but I don't know how far to go before I fill up the pool again. Pictures would be best, I know.
What should I do at this point?
How do I become a better scrubber?
Should I bleach and scrub until I see NO evidence of even dead algae (gray colored)? Bleach until the plaster is white again?
Should I rent a power washer and work on the plaster?
Do I scrub the plaster with trichlor pucks?
What do I do with the cartridge filter or will the higher FC levels sanitize that also.
Is there any hope? or should I give up?
Other info and questions:
The main drain is closed because of a major leak in the line. I removed the plate because debris were collecting under the plate and consuming FC? Can a main drain plate cover be closed better?
Debris are also collecting behind the light. Can this be closed without debris collecting there either? The light went out again and I don't use it much anyway - it just draws bugs to the pool.