all i said was check fc at end of day,I would think the missing ozone and increased UV would be harder on FC. But that, too, doesn't matter. Testing the FC will reveal the loss, adjusting the SWG will account for it. You might go through your SWG faster, but that doesn't affect the FC/CYA relationship. We think. That, too, doesn't really matter. Remember, these guidelines are guidelines. If you find that because of your pool, or your swimmer load or your location or your sun exposure of Uncle Sal peein' in the pool, that you need a little more CYA to offset the FC loss, then you add a little more CYA. If that helps, then you have your own FC/CYA formula customized for your pool. If it's 10 more than TFP says it should be, so be it. The opposite is also true. If you try a little less CYA one year and FC is maintained as usual, then you can use a little less than the rest of us. You don't have to drive yourself nuts with TFP numbers, or any of our advice, you only have to keep your pool good-to-go, and that's best done by you doing what works for you and your pool.