Aquarium Salt Dosage Calculator

How to Use This Tool

Follow these simple steps to calculate the correct aquarium salt dosage:

1. Enter your tank’s volume and select whether the measurement is in US gallons or liters.
2. Select the unit you use to measure salinity (ppt, ppm, or specific gravity) from the dropdown.
3. Input your tank’s current salinity level and your target salinity level for the same unit.
4. Select the purity of the salt you plan to use (99.9% pure aquarium salt or 95% pure standard salt).
5. Click the Calculate Dosage button to see the exact amount of salt to add.
6. Use the Reset button to clear all fields and start a new calculation.

Formula and Logic

This calculator uses standard aquaculture conversion rates to ensure accurate results:

• Tank volume is converted to liters first: 1 US gallon = 3.78541 liters.
• Salinity units are converted to parts per thousand (ppt) for consistency:
  • 1 ppm (part per million) = 0.001 ppt
  • Specific gravity (sg) to ppt: (sg - 1.000) * 1400 (valid for 1.000–1.030 sg range)
• 1 ppt equals 1 gram of salt per liter of water, so the dosage formula is: (Target ppt - Current ppt) * Tank Volume (L) / Salt Purity = Total Salt (grams)
• Final results are converted to grams, ounces, and approximate cup measurements for convenience.

Practical Notes

Keep these real-world tips in mind when using aquarium salt:

• Only use aquarium-specific salt for freshwater tanks—table salt contains iodine and anti-caking agents that can harm fish.
• Most freshwater community fish tolerate salinity up to 3–5 ppt; brackish water species may require up to 15 ppt.
• Always dissolve salt in a separate container of tank water before adding it to the aquarium to avoid burning fish gills.
• To lower salinity, perform partial water changes with fresh dechlorinated water instead of adding salt.
• Measure salinity with a reliable refractometer or hydrometer for the most accurate results—strip tests are less precise.

Why This Tool Is Useful

Over or under-dosing aquarium salt can stress or kill fish, so precise measurements are critical for home aquarium owners. This tool eliminates guesswork by accounting for tank size, current water conditions, and target salinity in one calculation. It saves time compared to manual conversions and reduces the risk of costly mistakes that could harm your aquatic pets. Whether you’re treating ich, adjusting for brackish species, or doing routine maintenance, this calculator provides reliable, actionable results.

Frequently Asked Questions

Can I use table salt instead of aquarium salt?

No, table salt often contains iodine and anti-caking agents that are toxic to fish over time. Always use pure aquarium salt labeled for freshwater or brackish tank use.

How often should I add salt to my aquarium?

Only add salt when adjusting salinity for treatment or species needs—most freshwater tanks do not require regular salt additions. Salt does not evaporate, so only add more when performing water changes that remove salted water.

What if my target salinity is lower than current?

This tool only calculates salt additions, not removals. To lower salinity, remove a portion of tank water and replace it with fresh dechlorinated water, then retest salinity until you reach the target level.

Additional Guidance

For best results, follow these extra guidelines when dosing aquarium salt:

• Test salinity 24 hours after adding salt to ensure levels stabilize, as substrate and decorations can absorb small amounts of salt.
• Quarantine new fish in a separate salted tank (3 ppt) for 2–4 weeks to treat common parasites before adding them to your main tank.
• Live plants and invertebrates (snails, shrimp) are sensitive to salt—remove them before dosing if salinity exceeds 2 ppt.
• Keep a log of salt additions and salinity tests to track changes over time, especially for brackish tanks that require consistent levels.