Hmmm - I'm thinking the chlorine is reacting more quickly to precipitate metals with the low cya. I have tried running my pool with a low cya, and did have more staining. This year I am trying to run a higher cya and see what happens. Maybe you can try getting some cya, and adding a little, this way you can use regular bleach so you can control the amount you are putting in. this way the chlorine can be raised gradually. I know how you feel about hating the pool I feel that way too sometimes, it is all a learning experience, and the stupid water doesn't always react the way it is supposed to . The only thing I know for sure is that high ph with high chlorine allows metals to fall out. The rest is trial and error. Even the amounts that are needed for the sequestering agent, and ph and chlorine can vary. I do find that using bleach does make staining less likely than using pucks or calhypo. I don't have any scientific proof, just my experiments that I have been trying from year to year. Don't get discouraged, you will find what works for your pool - I would also suggest adding more sequestering agent. Sometimes the water needs more than the directions on the bottle say. If you need more metal out, try a different one this time. I hope this helps, feel free to ask any other questions you have, and keep us informed. It is always a learning experience and we can learn from each other so we can post different ways of fighting those rotten stains