RO/DI makeup water

[Hobster]

Should RO/DI make up water be buffered before adding to the tank? When the water evaporates do all the elements stay in the tank or do some evaporate off? By adding the RO/DI water with no elements and low pH wouldn/t that eventually alter the balance in the tank or is it the same as SG going up when evaporation takes place?

[Randy Holmes-Farley]

No, there is no need to add anything to evaporation replacement water unless you choose to use that as a convenient way to dose some calcium or alkalinity or both (or something else that you've determined that you need or want).

Nothing leaves the tank via evaporation except water and some things that you do not care about (ammonia, some organics, gases, etc.)

SG goes up when water evaporates, and comes right back when you add replacement RO/DI water. :)