How to start

[Confused]

I have been reading all the advice given to people who are fighting the algae problem and understand I need to keep my fac at atleast 10 ppm for 24 hours. I shocked the pool last night and when I woke up (7) hours later and tested, there is still 0 fac. My test strip shows 0 cya so I am assuming I need to bring my cya up to atleast 50 before I can maintain the high fac level for 24 hours???? Ph is at 7.2, Ta is 120. Any advice is appreciated.

[Backglass]

Correct...if you have no CYA a free chlorine level of 20 can go to 0 in just a few hours of direct sunlight. At this point, ANY will help. You can boost your CYA some by using pucks in the skimmer (pump running 24/7). This is slow however. The fast way is to buy some CYA and add it via the sock method. CYA dissolves very slowly (up to a week) so you put some in an old sock and either tie it near your return or put it in your skimmer.

It is also very possible that the chlorine you added did it's job and was completely "eaten" by your algae bloom. During severe blooms, some people must add chlorine two or three times a day in order to keep ahead of the "green menace".

Probably a little of both.

[chem geek]

Another option for adding CYA at the same time as chlorine and to do so quickly is to use Dichlor powder/granules as these dissolve very quickly. For every 1 ppm FC you add with Dichlor you also get 0.9 ppm CYA. It's more expensive than the pure CYA, but if you have to shock with chlorine anyway, it's an option for you. Just be sure not to add too much -- stop when you've added about 33 ppm FC worth of Dichlor since that's 30 ppm CYA.