I have an 18,000 gallon above ground chlorine pool with a sand filter. Last winter the cover came off my pool and left my pool in a sad state when I attempted to open if this spring. I have been fighting with the pool all summer and only had a semi good conditions for about 2 weeks this summer. My water remains green at this time despite all the store bought chemicals I have placed in it. I'm trying to decide what would be my best options to close the pool for winter and hopefully start over again in the spring. I have put so much money in chemicals this year already and am hoping to find a cost efficient way to close and also open next spring. Any advice would be helpful.