Vince G.

I would say you are safe to put both the snails and plecos back into the tank whenever you feel comfortable. Nerite snails live in salt water so it does not bother them at all and I have treated tanks with salt up to 1tbsp per 3 gallons and had no issue with plecos being sensitive to it. When your removing salt from an aquarium you can just use the amount of water you remove as a judge for how much salt is left. If you changed out 30% of the water then you can assume 30% of the salt has been removed from the tank.