It all depends on what's in the tank. All of my tanks have water dechlorinated using Prime.
I have 90g, 29g, and 10g freshwater tanks that I use nothing else in,
a 60g planted tank to which I inject Co2 and add Flourish & fertilizing root tabs,
a 150g African cichlid tank to which I make my own cichlid salt mix out of baking soda + Epsom salt + marine salt,
and a 14g saltwater tank to which I add marine salt and a little baking soda.
There is no one size fits all when it comes to what to add for your fish, and on a general level it's usually not necessary to add anything (with freshwater), and doing so can sometimes complicate things and cause problems in an otherwise healthy tank.
What kind of fish do you have? Perhaps we can give you some ideas.