Aquarium Salt Dosing Calculator

How dosing rate changes by purpose

Use plain, non-iodized aquarium or kosher/canning salt (sodium chloride), never table salt with anti-caking or iodine additives. A light general tonic dose is common as a mild stress-reducer or for species that naturally tolerate brackish conditions. Treating fin rot or general bacterial irritation typically uses a somewhat stronger dose. Ich treatment uses the strongest common dose, and is specifically added gradually over 24–48 hours in three smaller doses rather than all at once, to avoid shocking fish with a sudden salinity change.

Species that don't tolerate added salt

Scaleless and thin-scaled fish (many catfish, loaches, some tetras), most live plants, and many invertebrates (snails, shrimp) are sensitive to added salt, sometimes severely. Research your specific livestock before dosing salt into a community tank, and consider a separate hospital tank for salt-based treatment if your main tank has salt-sensitive residents.

Salt doesn't evaporate — only water changes remove it

When water evaporates from a tank, the dissolved salt stays behind, so topping off with plain water doesn't dilute it and repeated evaporation actually concentrates it further. Only a water change (removing salted water and replacing with fresh) reduces the salt level. Keep this in mind when a treatment period ends and you want to return to a salt-free tank.

Source: Dosing rates reflect commonly published freshwater aquarium-salt guidelines used across fish-health hobby references for tonic, treatment and ich-treatment use.