Thank you for your comments!
Here is an explanation :
I have a cottage too far to visit it every week, so I need some automation and monitoring.
Salt water - Agree - it is the way to go but it will raze PH.
So I need a system to lower ph if it is too high as well as to check chlorine level.
I can use Arctic Spa Boy system to monitor and control chlorine level but it does not inject Ph decreaser.
So why do not use Fully automated PH controller used for aquariums ?
Simple, cheap and ready to go solution.(it has dossing pump)
Just an idea at the moment.
Thanks!