I appreciate the assistance. So I am just going to go with chlorine. I am just starting to figure out what I need by searching around the site. I have the previous owner's pool person coming in the morning to open the pool. I know nothing about pools and haven't even figured out how to take the automatic cover off. It is in ground fiberglass. It was probably closed last October (northern Michigan close to Canada). Is there anything I need to do to switch from Pristine Blue (chemicals left in the pool?) Or anything else I need to be aware of?

Thanks!