That depends. Green Treat will only kill the algae present. After cleaning the green algae you will need to rebalance and correct any issues that led to the algae growth. To prevent algae we recommend using No Mor Problems.
Yellow Treat will only kill the algae present. This should afford you at least a few days of algae free pool to correct balancing to keep algae at bay. To prevent algae we recommend using No Mor Problems.
After using Yellow Treat your chlorine reading should return in 24 to 48 hours. Times may vary. If it hasn't come back in a few days, open a support ticket and we'll diagnose why it's taking so long, and how to speed up the process.