Oops! I read the cya as the alkalinity, down from 120 to 100 Sorry. Yes, you can wait till next year to clean up the stains - they will come off then, and maybe they will go away over the winter. You can get your water tested at some pool stores, or you can sometimes get it tested by your city. Where does your water come from? If it is from a well, then you will need to get it tested on your own, if it is city water they should be able to tell you what is in it. You won't need anymore cya regent until next spring. If your cya has been running around 30, then you are at the low end of cya and even if you are using trichlor pucks you probably didn't come up much. If I were you, I would close the pool this year, and before you open next year get some ascorbic acid, sequesterer, and new regents so you will be ready to go. You can do the stain treatment before you get your whole pool balanced, this way you will only have to do it once. As soon as it opens, take care of the algae (if the water is green) first. Then check to see if there is stains - I have opened to a stainfree pool every year, even if I had some at the end of the summer before. If you do have stains, do the stain treatment with sequesterer. Then balance the water, then have a wonderful summer