Recurring algae, high phosphates

[Luric]

I'm ready to drain & refill (or maybe just fill in) I can't figure out what is happening. I thought it was mustard algae, so I did that version of SLAM, passed all the hurdles, then kept my FC 8-10. Everything was fine, until I woke up one morning and it was 5. Then the mustard spots showed up again. I caught early and it didn't take off like last time, but it's still not quite sparkly and there's still algae eating the chlorine. I'm wondering if it's black algae? Or whatever type trapped in a place I can't reach? Our light screws stripped, so we had to have someone come in last year to repair, and he permanently affixed them - they can be removed but not with any equipment we have. Was our best option at the time since no one really likes to see a light float to the top of the pool while you're swimming. I get they're still safe, but it's also still really unsettling: electricity/water. Our phosphates are crazy high as we never cover the pool which is surrounded by landscaping which sits and decompose through the off-season, plus everything that falls in through out the summer. We've treated with phosphate remover but not made much headway. Knowing that's a fuel for algae, wondering if it makes more sense (time, energy & $$) to just drain, clean & refill? We have a black bottom pool, so it's really hard to tell if maybe there's black algae somewhere. Even during summers when the pool did sparkle, any time I brushed small plums of dust (?) would rise & settle. I feel like there's just so much gunk imbetted in our pebbletec that just needs to be acid washed or however you clean it and then start fresh. I could replace our stripped lights once & for all as well. We also have a raised waterfall with a 3ft deep well. I do brush that when I'm SLAMing, but I just noticed how yellow the rocks behind (hidden by japanese maple) are. Could that be the source? We also have a bunch of black dots on the diving board - maybe that's the problem? They don't seem slimy. A pool toy or suit?

For now, I'm planning to just try to maintain the high FC. Should I continue to let it drop and do it's thing during the daylight and bump up again when it's dark? Or raise now knowing I’ll lose a lot just to sun? Should I do a phosphate treatment to try to cut food source? Or quit and find a new hobby?

I'm attaching a few photos from yesterday to hopefully better explain (plus one from when it’s “normal”) Will try to add a current shortly

FC: 23
CC: 0
TA: 90
pH: 7.5
CH: 300
CYA: 60 (<--had been 40 and after I "finally" cleared the last algae outbreak few weeks ago I slowly started to raise, aiming for 70-80, but have stopped now)
Salt: 3700
Phosphates: over 4000 (yes thousand)

 

[Mdragger88]

No need to fill it in just yet
Lets be sure you do this
SLAM Process thoroughly then after passing all 3 end of slam criteria:
CC is 0.5 or lower;
You pass an Overnight Chlorine Loss Test
AND
The water is clear.
(Crystal Clear w/no algae dead or alive)
Raise fc to MA slam level for 24 hours & follow all the protocols here:

Mustard Algae

Today We are going to show you how you can get rid of mustard algae in your pool. By following the steps in this guide and with no expensive chemicals.

www.google.com

After which you may want to maintain MA minimum for some time as insurance (maybe from here on out)
During the slam
*Check & scrub every nook & cranny where algae may hide (light niches, steps, drain covers, ladder handrails, skimmer throats/weirs, abandoned lines, autofill, overflow drains, etc.)
*If water can go there, algae can thrive there.
*Run slam level water through all water features & lines for at least a couple hours a day during the SLAM Process.
*Brush & or vac daily (this breaks up biofilms that algae uses to protect itself from chlorine)
*Backwash/clean filter when pressure rises 25%over clean pressure.
Since you can’t get the light out of the niche you may need try to get creative & flush the niche out as best you can through the gaps that it looks like may be there. When people can’t get their drain covers off we recommend squirting some bleach directly in there. For the light I would suggest you dilute it then flush it with water after a few minutes. Keep the Light off.
The one red bush thing or anything else that overhangs the water should probably be cut back.