Meant to bump this thread last week but never got around to it. Things are all good in my hood again but I'll be Darn if I didn't get another algae bloom and had to SLAM my pool again. As before, I'll give a breakdown of test results and the ensuing pattern:
| April 16 (FC high, turned down SWG a bit) | April 28 | May 3 8:00 p.m. (visible algae) | May 4 6:00 a.m. (failed OCLT) |
FC | 9.0 | 7.5 | 6.5 | 5.0 |
CC | 0.0 | 0.0 | 0.5 | 0.5 |
pH | 7.5 | 7.8 | 7.8 | |
CYA | 50 | 50 | | |
We were noticing the same green spots collecting in the same areas as before (photos on page 2) around the first of May, along with the puffing while brushing. Have never seen it it on the walls at all, just the floor/shelf/stairs. I really had myself convinced it was pollen until it failed the OCLT.
So on May 4 I dropped the pH to 7.2 and added chlorine to get it to 20, kept up with it rigorously for a couple of days and considered myself to have completed the SLAM after a successful OCLT from May 6-7th. Been letting the FC drop gradually since then and the water remains clear with no further algae appearing in the typical areas.
All in all really not too painful, just annoying and frustrating. There is essentially nowhere for algae to be hiding and I'm clearly well within, in fact more so at the upper end of the recommended range of free chlorine. I may try and remove the weir door to more closely inspect and thoroughly scrub it. Dead spots in the pool perhaps? I could redirect the returns and/or adjust the suction valve to draw more from the main drain (probably 80% skimmer currently), but that would all just be a guessing game I suspect. I also run the pump at a very low speed most of the day, I could bump that up (along with my power bill) if the thought is that more circulation could help.
I also just after this SLAM added boric acid to get my borates to around 35 or so and will likely use some borax to go a little higher. I don't expect that alone to solve the problem, but understand it
might help prohibit algae growth.