This is from tropical aquarium mag and a IBC members insite on salt.
Here’s what I read.
There are almost as may opinions about salt in fresh water tanks as there are experts.
Salt will encourage slime coat on damaged or diseased tissue but it’s an irritation response. If the fish is healthy and already has a slime coat then why add salt?
Salt will not reduce the buildup of nitrates, but will reduce nitrite uptake.
Salt inhibits fresh water parasites so Ich and Velvet incidence may be reduced. If you maintain healthy water conditions these should not be a problem though.
A tonic level of salt by the experts is anywhere from 1 teaspoon to 1 tablespoon per gallon of water(quite a range).
My thoughts as a result of the above.
Fish body fluids are at about 0.9% or 9 ppt (parts per thousand) and fresh water can have up to 0.05% or 0.5 ppt. Adding salt at 1 teaspoon per gallon would add about 2.4 ppt
while 1 Tablespoon per gallon would add over 7 ppt. Fish clear wastes from their system by taking in water through osmosis and expelling them as urine (approximately 1/3 body weight per day) and the addition of salt will make the fish less hypertonic thereby reducing the rate of exchange. I guess personally I would opt to not use the salt and keep the flushing action maximized because they do not drink water, and keep the water clean to help reduce stress and minimize disease potential.
I think I’m going to research this some more