Thought I had chemistry under control, but a week away and returned to find crawler hung up on thermometer cord. Bottom of pool covered in green slime. This tells me that I have had an algae bloom, but was simply vacuuming it up. Need to kill this stuff off for good.
Challenge: 45,000 gallon pool, CYA is probably north of 150 (scale on test kit tube doesn't go that high; my best guess). SLAMming would require enormous amounts of chlorine (25 gallons at 11% concentration at current CYA levels); perhaps too much. Ideally I would drain and refill, but we're in the middle of a drought here in northern CA and such things, while not yet prohibited, are not encouraged. Further, if I drain and refill, I do not know how to eliminate whatever algae might be in the cartridge, or how to kill whatever is left stuck on the pool walls.
So: SLAM or drain/refill and deal with the walls and cartridge? Any and all suggestions appreciated; I'm a rookie pool owner. Many thanks.