Closing....when to add algaecide?

[JimK]

I read not to add algaecide right after shocking because the chlorine would break down the algaecide. The article said to shock a couple days before adding the winter algaecide.

A "couple days before" seems pretty vague given it doesn't state a shock level. So my question is, how low should I let the chlorine drop before adding the winter algaecide?

My CYA level is about 80, so my shock level would be about 21 if I understand correctly. Chlorine demand is pretty low right now with the colder water temps so it would probably take more than a couple days for the chlorine to return to "normal" levels (about 5ppm).

My other levels are:
pH - 7.5
borates - 60
TA - 90
CC - 0

Thanks.

[CarlD]

What I do is bring my FC up to shock level, then I put in a quart of 60% Polyquat algaecide. I wait 48 hours for the FC to drop, then test the water, and add chlorine to bring it back up to shock level. Then I close. This generally keeps me from having a problem in the spring, if I open early enough.

[JimK]

What I do is bring my FC up to shock level, then I put in a quart of 60% Polyquat algaecide. I wait 48 hours for the FC to drop, then test the water, and add chlorine to bring it back up to shock level. Then I close. This generally keeps me from having a problem in the spring, if I open early enough.

Thanks for sharing your experience.

Supposedly, according to what I read, high chlorine levels break down the algaecide, hence my question. I guess what I'll do is shock then wait until chlorine drops back down to a "normal" level (about 5ppm in my case with CYA at about 80) before adding the winter algaecide.