Automatic top off question

[JoeA]

I am researching DIY auto top offs and..... well dumb question but is the water you add to the tank or sump via the auto top off fresh water or salt water? I know the water evaporates but the salt dosen't correct?

[revhtree]

Correct! The top off water is fresh water. Of course treated for chlorine.

[jaiden]

add to the sump if you have one.. with an overflow, the water level in your tank should never drop at all, so autotopoff is not an option there. a sump is the perfect place for one.