Use this aquarium salt dosing calculator to find the correct amount of aquarium salt for your freshwater fish tank. Enter tank volume, water volume removed, and target treatment level to get the exact tablespoon and teaspoon measurements to add.
Salt Dose Calculator
Enter water removed before adding new water and salt
How to Use Aquarium Salt Safely
Aquarium salt is one of the most effective and affordable treatments for common freshwater fish diseases and stress. Used correctly, it improves osmoregulation, inhibits external parasites, and supports slime coat production. Used incorrectly, it stresses salt-sensitive species and is impossible to remove quickly.
How to Add Salt to a Tank
Dissolve the calculated amount of salt in a cup of tank water before adding it to the aquarium. Never add salt directly to the tank — undissolved salt crystals can concentrate near the substrate and burn fish or invertebrates. Add the dissolved solution slowly to one end of the tank while circulation distributes it.
Salt and Water Changes
The most common mistake is re-dosing salt for evaporation top-offs. Salt does not evaporate — only water does. When you top off for evaporation, do NOT add salt. You only add salt when you do a true water change (removing tank water). The calculator accounts for this: enter how much water you removed and how much you're replacing, and it calculates only the salt needed to bring the new water up to target concentration.
Species Sensitivity
Most common community fish (guppies, mollies, platys, goldfish, bettas) tolerate Level 1–2 salt well. Be cautious with: corydoras catfish, otocinclus, most tetras (neon, cardinal), loaches, freshwater invertebrates (shrimp, snails), and live aquatic plants. For sensitive species, use Level 1 only and monitor closely.
Frequently Asked Questions
Is this aquarium salt calculator free?
Yes, completely free with no signup required.
What aquarium salt level should I use for ich treatment?
For ich (Ichthyophthirius multifiliis) treatment, use Level 2 (2 tablespoons per 5 gallons / 1 tsp per gallon). Raise temperature to 82–86°F alongside salt treatment and maintain for 2 weeks after the last visible spot disappears.
Can I use table salt or sea salt in a freshwater aquarium?
Do not use iodized table salt — iodine is toxic to fish and aquatic invertebrates. Plain non-iodized salt (canning salt, kosher salt) works in a pinch. Dedicated aquarium salt (API Aquarium Salt) is safest — it has no additives. Do NOT use marine/reef salt in freshwater tanks; it changes water chemistry dramatically.
Is aquarium salt safe for all freshwater fish?
Most freshwater fish tolerate low levels of salt well. However, some species are salt-sensitive: corydoras catfish, otocinclus, most tetras, discus, and freshwater plants are sensitive to higher salt levels. Avoid Level 2–3 dosing with these species. Level 1 (stress relief) is generally safe for all freshwater fish.
How do I remove salt from my aquarium?
Salt is removed through water changes. Unlike other additives, salt does not evaporate or break down. When water evaporates, the salt stays behind — so only replace salt when you do actual water changes (removing water), not when you top off for evaporation. Do a series of 25–30% water changes to gradually reduce salt concentration.