Calculate the exact salt required for your tank volume, desired dosage, and water-change replacement. Visualize salinity and mixing in real time.
Total water volume of your aquarium (not tank dimensions).
Please enter a valid volume greater than 0.
Always follow the salt product’s instructions. Typical: 1 tsp/gal (freshwater bath), 1 tbsp/5 gal (general tonic), or 35 g/L (marine).
Please enter a valid dosage (0 or greater).
If you already added salt, enter the amount to avoid over-dosing.
Volume replaced during a water change. Salt needed to re-dose replacement water.
Tank Volume
Salt Measure
Salt Required
—
tsp
Salt per Unit
—
tsp/gal
Replacement Water Salt
—
tsp
Total Dosage (Tank + Change)
—
tsp
Unit Conversions
Important: Dosage depends on species, salt product, and purpose. Always follow the exact product instructions and consult a vet for treatment. This tool is for estimation only.
Mixing Indicator
Dissolve salt thoroughly before adding to tank. Stir gently.
Aquarium salt (often sodium chloride, NaCl) is used in freshwater aquariums to support osmoregulation, treat mild infections, and reduce stress. It is not the same as marine salt mix, which contains a full spectrum of minerals (magnesium, calcium, potassium, etc.) needed for reef tanks. Using table salt with anti-caking agents or iodine can harm fish — always use a product labeled for aquarium use.
Dosage is highly species-dependent. Scaleless fish (loaches, catfish) and live plants are sensitive; goldfish and koi tolerate higher concentrations. The product label is your primary guide, and this calculator helps you scale that dosage to your actual water volume and water-change routine.
When you perform a water change, you remove both water and the salt dissolved in it. To maintain your target salinity, you must re-dose the replacement water. The basic formula is:
If you are treating the whole tank, use the first formula. If you are only re-dosing replacement water during a routine change, use the second. Our calculator gives you both, plus a total that reflects a full treatment plus a water change.
| Species / Group | Typical Tolerance | Notes |
|---|---|---|
| Goldfish / Koi | 0.1–0.3% (1–3 tsp/gal) | Tolerate higher concentrations for treatment. |
| Livebearers (Guppies, Mollies) | 0.05–0.1% (0.5–1 tsp/gal) | Mollies appreciate slight salinity. |
| Tetras, Rasboras | 0–0.05% (0–0.5 tsp/gal) | Very sensitive; use only if directed. |
| Scaleless fish (Loaches, Catfish) | Avoid or 0.02% max | Salt can damage their skin and gills. |
| Live plants | 0–0.05% | Many plants melt with any salt. |
| Marine / Reef | 3.5% (35 g/L) | Requires marine salt mix, not aquarium salt. |
Always research your specific species. When in doubt, under-dose or consult a qualified aquarist or veterinarian.
Common dosage: 1 teaspoon per gallon for a short-term bath, or 1 tablespoon per 5 gallons for a general tonic. For marine tanks, 35 g/L (approx. 1.026 SG). Always check your salt product label — concentrations vary by brand and intended use.
No. Table salt often contains iodine and anti-caking agents that can harm fish and invertebrates. Use only salt labeled for aquarium use, or pure sodium chloride without additives.
Multiply the volume of water you are replacing by your desired dosage. For example, replacing 10 gallons at 1 tsp/gal requires 10 tsp of salt dissolved into the replacement water before adding it back to the tank.
No. Scaleless fish (loaches, catfish), many tetras, and live plants are sensitive or intolerant. Research your specific species before adding salt, and never use it as a substitute for proper quarantine or medication.
Salt does not evaporate, so it stays in the tank. Only re-dose the amount removed during water changes. Over time, salt can accumulate if you top off with salted water — always top off evaporation with fresh water.
Aquarium salt is primarily sodium chloride. Marine salt mix contains sodium chloride plus magnesium, calcium, potassium, and trace elements to replicate seawater. They are not interchangeable for saltwater tanks.
Yes, for estimating grams of marine salt mix to reach a target salinity (e.g., 35 g/L). However, you should always use a refractometer or hydrometer to verify specific gravity — this calculator is an estimate only.
Perform a partial water change with fresh (unsalted) water to dilute the concentration. Monitor fish behavior and test salinity if possible. For severe overdoses, consult a veterinarian or experienced aquarist.
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Disclaimer: This aquarium salt dosage calculator provides estimates for educational purposes only. Actual dosage depends on fish species, salt product concentration, tank conditions, and intended purpose. Always read and follow the manufacturer’s instructions and consult a qualified veterinarian for disease treatment. MyEasyCalculators is not liable for any harm to aquatic life resulting from the use of this tool.