RO/DI Unit for a 75 gallon tank?

[dave green]

I'm not really sure how these work... do you install these as a part of the tank or hook them up to a garden hose and fill a bucket, etc...?

 

[zdaytonaroadster]

u install them and they make pure water, you then mix you salt into it and then pour it in your tank.

Its like a super britta water purifier