In your pool, a quart of 6% bleach will add around 2.5ppm of chlorine. So, once your CYA is somewhere between 30-50 and you go to testing chlorine in the evenings only, you'll just use that as a reference to figure out how much to add to take your chlorine level back up to around 6. If you find that by the next evening, your chlorine level has fallen below 3ppm, then you'll want to add enough bleach to get to 7ppm. You'll soon learn how high you need to take the chlorine each evening to make sure you don't fall below 3 by the following evening.