Since you only lost 0.5 chlorine overnight, that is good. It is normal to lose chlorine to the sun, but when you lose large amounts overnight when there is no sun, it is an indicator that you are fighting something. Since you lost less than 1ppm, it tells us that it is pretty certain that you have that algae bloom licked. But, you do need to add chlorine this morning. With your CYA level, you must keep the chlorine between 8-15 ALL THE TIME. If you let it drop below that, an algae bloom will start.
You don't show your volume, so I can't comment on bleach amounts. But, if you go to the Forum Q & A section, there is a thread called 'Bleach Calculator.' I think it is in the third post in that thread, there is a link so you can download a calculator. It has more than just a bleach calculator. In the upper left hand corner, there is a drop down with other calcs as well.
What you want to do is add enough bleach to get back up to 15. Then, test tonight. Again, add enough bleach to get back to 15. Then, tomorrow evening, see where you are when you test. If you are below 8, then you will want to take it just a little higher. My guess is that if you add enough bleach to get to 15, you should be able to make it a couple of days without adding more bleach. That is one benefit to having a high CYA pool.
I'm hoping that your chlorine loss will slow down and that your higher usage the other day was just a result of the recent algae bloom you were fighting. The key is that you can never let your chlorine drop below 8ppm.
Keep us posted how things are going and let us know if you have further questions.
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