Do I HAVE to add shock to close?

[waste]

You can trust physics to distribute the algicide (algistat - more properly) after the pool is covered, but I'd trust the filtration system to better disribute it throughout the pool. Shocking is something that may or may not be neccessary, but is a good idea, it kills any little stuff that may try to grow over the winter.

[traceyb]

I asssume you should put the filter on "circulate" so that you don't filter OUT thee algaecide 60?

[waste]

Yes, as long as the water is ~clean, just 'recirc'