How to keep blue water when winterized?

[makomermaid]

My pool guy came and winterized the pool by blowing the water out of all the pipes (including an outdoor bathroom) and then turned off the pump. We do not have a pool cover because we have no trees and don't want to spend the money on one right now.

My question is this:

Is there anything I can do over the winter (having no pump) to prevent the water from turning green?

 

[jeffchap]

Add bleach and stir it up manually with a net. You shouldn't need to do it too often. Chlorine use goes way down when the water is below 60 degrees. Once a week might be plenty.