You have to add chlorine as often as it takes throughout the day to hold your pool at shock level. For my algae battle, it was every couple of hours on the first day. The next day it was maybe every 4 hours. The day after that, it was maybe every 7-9 hours. If you are adding chlorine only once a day, you are not getting ahead of your problem. In fact, you are probably just wasting time and money. You have to be very persistent.