I have done enough reading on here to know that the only way to lower CYA significantly is to drain and refill. We set up our pool the 2nd week in July. I added two containers of stabilizer ( purchased at pool store, do not remember what size but it was the amount that was recommended by the store). Initially was only using test strips until my TF100 arrived. The strips did not show any CYA and the three times that I have tested with the kit has also not shown any. I do know that I need to add stabilizer but what would cause the level to drop drastically or not register at all? I had posted a few weeks ago about cloudy water but that has since cleared up. My FC readings are usually in .5 to 2.5 level but it is hard to regulate w/o a CYA level.