Salinity levels (freshwater)

[Deminox]

Just got my InstantOcean brand salinity meter. Measures salt and gravity. Obviously its designed for salt water, but i want to make sure when i add aquarium salt to the tank during water changes i don't go over a safe threshold. Anyone know what that threshold is? Ive seen formulas for calculating how much to add based on tank size, how full, and substrate.. but nothing really on "what parts per million is safe for goldfish / pleco"

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[coralbandit]

Full marine is 1.020-1.025
Brackish is around 1.009-1.0013
Fresh water reads 1.00 (on my digital checker).
I can't remember the lowest level is on your hydrometer.
For prophalatic use salt is best around 1 teaspoon per 5g with higher levels running into medical usage.
Add regular dose to water replacement during changes but NO salt in water for evaporation replacement.
Salt does not evaporate.