Dave i think ur rong all my fish are freshwater and i put in salt. iamgroovey salt protects heals and hatches brine shrimp.i think u shood put some in just to protect them for diesase.
Brine shrimp aside, this is an extremely prevalent myth in our hobby and is one that many folks defend strongly. However, if you do some research into the proffessional side of the hobby i.e. fish breeders, public aquariums, and fish farms. You will find that the folks who make a living raising freshwater fish do not use salt regularly. You will also find a huge amount of good science that kills the salt myth entirely.
Additionally, if you calculate the numbers you will find that no freshwater in the world including the rift lakes comes close to the 1 tablespoon per 5 gallon reccomendation made by the salt sellers.
With rift lake fish, there are mineral mixes available to simulate the natural environment of those fish. These are often termed as Cichlid salts, but should not be confused with pure NaCl. Cichlid salt mixes are mineral salts designed to create hard water and in the right circumstance are quite useful.
Reef salt is not pure NaCl either, and few reef keepers have any use for aquarium salt as sold in stores. it doesn't do a good job of simulating brakish or sea water either.
Essentially freshwater aquarium salt is a poorly marketed product with limited uses, that creates a lot of problems in our hobby. It is very usefull for specified treatment of disease short term. The real kicker is the tablespoon per five gallon dose reccomended is too much for some things and not enough for others.
The idea of enhancing slime coat, or healing wounds and fungus sort of flies in the face of reason. Healthy fish will produce the slime coat they need, unhealthy fish need to be treated directly not subjected to long term unnatural environments. Keep your tank clean, feed your fish good nutrition and provide them with an adequate environment, and they will stay healthy without salt for well past their normal wild lifespans. If you have hard water fish and wish to go to the trouble, add calcium and magnesium, if you have soft water fish work on keeping TDS levels low for them. Either way Salt does not add up to healthy normal fish keeping.
Dave