Sun burns through chlorine fast, so shock in the evening/after sundown so it works all night. CYA in the water protects it somewhat, but evening is still the move.

Algaecide goes AFTER the shock, not before — high chlorine breaks down a lot of algaecides (hence the foam). Let your FC come back down to normal, then add it if you still need it. Foam will dissipate on its own.

Yeah it degrades slowly, roughly 3-5% a month is normal and faster in hot/sunny weather. Splash-out and backwashing lose some too. Topping up mid-season is totally normal.

I swear mine disappear over the winter (9 month in mn) several years I was close to 0 after being above 30ppm

Put it in a sock in the skimmer or hang it in front of a return — takes a day or two. Don't dump granular CYA on the pool floor, it can etch plaster. And it doesn't gate swimming, you're fine to use the pool while it dissolves.

sock in the skimmer, got it. thanks

Yep calcium scale. Pumice stone works on tile and plaster (NOT vinyl or fiberglass), or a scale remover product. Long term keep pH around 7.2-7.6 and keep an eye on calcium hardness — high pH + high CH is what deposits it.

Roughly a quart of muriatic brings 8.2 toward ~7.5 in 15k. Pour it slowly in front of a running return. You can swim once it's circulated, ~30 min, no need to wait hours. Double-check pH with a drop kit though, strips are rough on the high end.

Low and slow is the trick. A low rpm for 8-12 hrs gives you the same turnover way cheaper than high rpm for a few hours — power draw climbs steeply with speed. I only bump to high for an hour to run the cleaner.

switched to running low like this, bill dropped a noticeable amount

What are your numbers? Post a full set if you can — FC, CC, CYA and pH at minimum. Can't give you a SLAM level without knowing your CYA.

just tested: FC 2, CC 1.5, CYA 50, pH 7.8. it's straight up pea soup

CYA 50 means your SLAM FC is 20, and you're sitting at 2 — that's why nothing's happening. Get it to 20 and HOLD it there: retest and re-dose every couple hours, brush daily, pump 24/7. It'll go green → cloudy → clear over a few days.

day 5 and it finally passed an overnight chlorine test, water's clear. that was brutal lol. thank you

Take a sample to the store for a real salt number first — the cell's own reading drifts as it ages. If salt's actually fine, pull the cell and look for white scale on the plates, clean it with the acid ratio in your manual. 3 years is about when mine needed it.

pulled it, plates were crusted white. cleaned it and the error's gone for now

they don't last forever though, might want to start budgeting for a replacement