[doctor T]

Just curious about this. When we lose water (and salt) through evaporation why do we not add salt water to top off the tanks? It is obvious the salt is being removed through "creep" so why is it that every where I read, the guide is to top off with unsalted water.
I have not found an answer to this and I am curious.
Regards to all and kudos to the founders of this forum.

[WorkinMan]

Topping off with salt water adds more salt than is lost in creep alone and will raise your SG. During evaporation only water evaporates and the salt stays behind so only fresh water need be added to maintain the proper SG. It's kind of like if you have hard water and fill a glass with it, then set it on the counter and let it evaporate. The water evaporates and leaves a film on the glass (the film being all the dissolved minearls that made the water hard in the first place). Besides, most cases of salt creep happen from splashing water so no splashing water=less creep.

[mtfabel]

Salt does not evaporate only the water does so actually your salinity goes up a little as water evaporates just not enough to make a difference. But that is why.