Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Sodium chloride is not useful to plants.
Some fish seem to do better when there is a small amount of salt in the water, but if the GH and KH are right, then the salt is optional.
There is no need to add salt routinely, especially not to water you are using to top off the tank. Topping off implies that you are replacing water that has evaporated. Salt and minerals do not evaporate. They stay in the tank. The best way to replace evaporated water is to use reverse osmosis or distilled water. If you keep adding more salt to the tank with every top off the level can keep on climbing.