Novice tropical fish owner.

[Cindyloo]

Though this is widely debated among those that keep livebearers like platies and guppies, the addition of a little aquarium salt into the water helps keep them healthy. I'm not completely sure about the amount to add but that info is out there on the internet I'm sure. If you have a mixed tank with other fish that cannot tolerate salt it is not a good idea to add it to the tank. Hope this helps!

[HillSlugger]

Though this is widely debated among those that keep livebearers like platies and guppies, the addition of a little aquarium salt into the water helps keep them healthy. I'm not completely sure about the amount to add but that info is out there on the internet I'm sure. If you have a mixed tank with other fish that cannot tolerate salt it is not a good idea to add it to the tank. Hope this helps!

Growing up, between me and my brother we once had 7 fish tanks.

I think that one tablespoon of course salt per 5 gallons in a tank of mixed fish is about right. See this article.