I added some stabilized shock yesterday that really moved the chlorine level up and it held overnight so I guess I am fine now. But if CYA is of no benefit then I will not be adding any more. I'll just chlorinate w/bleach and see if it holds. Perhaps I just didn't get it up high enough or it was still working out bits of Baqua-crap. Yesterday I did notice some crap on the floor and seats and vacuumed it out. Looked kinda like sand but could have been some other sludge. I really only use my tub at night an usually only keep 1/2 of the cover off so I don't get much if any sun exposure.

Thanks for all the info.