Fry and Salt
Hello Tiger...
You're asking a very "loaded" question. I add a bit more than a teaspoon of standard aquarium salt to every five gallons of my water change water and replace at least half the tank water weekly. I've found over the years, my fish do better with it. The fry in my tanks do fine with a little salt.
I keep large tanks of "Livebearers", that also include a good number of different species of Corydoras. This amount of salt is really minimal and my plants do fine with it. I think a little standard aquarium salt has it's benefits for the fish in general.
But, I understand tropicals will do fine without it.
Just one fan of using salt in the freshwater aquarium.
B