dechlorinator, probably not, but then again you rarely suffer for using a water treatment product either.
solar salt is regular sodium chloride, at very low concentrations it is frequently argued that it can be beneficial for freshwater fish
Using salt in the freshwater aquarium - Algone
while i don't necessarily agree with the resulting conclusion of the page, it does very thoroughly discuss the topic from both sides.
i would argue table salt is a terrible thing to add to an aquarium, however aquarium salt (potassium chloride not sodium chloride) can have some positive benefits under specific conditions. though should be avoided in the planted tank. i once bought a water dechlorinator with "fish aid" that killed nearly 300$ worth of plants in a single dose. it wasn't until after i researched the product in detail that i discovered the "fish aid" was regular sodium chloride not potassium chloride as i had assumed.
a warning of note, water softeners usually make higher concentrations than are beneficial for freshwater fish, you would need to evaluate your own water to determine its potential for good or bad.
salt at any concentration is much more detrimental to planted aquariums as freshwater plant species are, broadly, more susceptible to osmotic pressure
and never ever use iodized salt (not really an issue in your case, but still... i'd hate for someone to do that to their fish)
it is possible to change the salt filter of most water softeners with a potassium filter (they're more expensive which is why most people don't use them). the effect on your water will be the same, but it will be more safe for aquariums.