How much aquarium salt per gallon?

A common mild dose is about 1 gram per liter, which is roughly one tablespoon of salt per 3 US gallons. For treating ich or stress, 2–3 grams per liter is used short-term. Always calculate from your actual water volume.

What kind of salt should I use?

Use plain non-iodized salt such as aquarium salt or kosher salt, with no iodine, anti-caking agents or additives. Do not use marine (reef) salt for a freshwater tonic unless that is specifically what you want.

Does aquarium salt evaporate?

No. Water evaporates but salt stays behind, so topping up with fresh water does not remove salt. Salt only leaves the tank through water changes, so only re-dose for the water you actually remove and replace.

How Much Salt to Add to a Freshwater Aquarium? (Dosage Chart)

Plain salt is one of the oldest and cheapest tools in fishkeeping. Used correctly it reduces stress, helps with some parasites, and eases nitrite problems. Used carelessly it harms salt-sensitive fish and plants. The key is the right concentration for your exact water volume — not a random handful.

Aquarium salt dosage chart

1 g/L — Mild general tonic (≈ 1 teaspoon per 5 L, or ≈ 1 tablespoon per 3 US gallons).
2 g/L — Moderate dose for ich and stress, short-term.
3 g/L — Stronger treatment dose; keep it short, then remove with water changes.
Above 3 g/L — Use with caution; above 5 g/L only as brief dips while watching fish closely.

Household spoons are only rough guides because salt grain size varies. For an exact amount, measure by weight or use a calculator based on your tank volume.

Calculate exact salt for your tank (free) →

How to add aquarium salt safely

Know your real water volume. Subtract substrate, rocks and décor from the tank's rated size. Our salt calculator also works out volume from length × width × height.
Dissolve the salt first in a cup of tank water, then pour it in gradually over a few minutes.
Re-dose only for water you change. Salt does not evaporate, so after a 20% water change, add salt only for that 20%.
Observe your fish. If they show distress, do a water change to dilute.

Which fish and plants are salt-sensitive?

Go low and slow — or avoid salt — with scaleless fish (many catfish and loaches), small tetras, and most live plants, which can suffer even at tonic doses. Hardy livebearers and many pond fish tolerate salt better. When in doubt, start at the low end.

Frequently asked questions

Can I keep salt in the tank all the time?
A permanent low dose is sometimes used for hardy fish, but it is not necessary for most freshwater setups and is not suitable for plants or scaleless fish. Treat, then remove via water changes.

Is table salt okay?
Only if it is pure sodium chloride with no iodine or anti-caking agents. Many table salts contain additives, so aquarium or kosher salt is safer.

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