He crystal clear water last year and this is how it opened

[SirSwimAlot]

I had brought chlorine to SLAM levels and used algae prevention (only non-TFP chemical I used all year).

How could I have prevented this? I'm removing the cover and going to start a SLAM.

The process I am going to do:

Reinstall plugs to pump basket and filter
Remove plugs from jets and skimmer
Skim pool for any visible debris (shouldn't be much as I skimmed it really good before cover)
Put DE in skimmer (it was backwashed then not filled at closing)
Run filter for 1 hr
Test cya, ph, then chlorine, TA, and Finally Hardness
Raise cya to 30
Raise chlorine to 12
Once some progress is made, test ph
Run rest of SLAM process

 

[zea3]

Timing is everything, or at least a big part of the thing. Close as late as you can, preferably after the pool water is consistantly below 60 degrees. Open as early as you can, preferably before the water reaches 70 degrees. If you have a mesh pool cover that can let fine debris through that can trigger an algae bloom if you close too soon or open too late.