How to Use the Aquarium Salt Dosage Calculator (Therapeutic)
This calculator computes the precise amount of aquarium salt needed to achieve therapeutic concentrations (0.1-0.3%) for treating common freshwater fish ailments like ich, fin rot, and stress. It eliminates guesswork and prevents dangerous over- or under-dosing.
Enter your aquarium's total volume in gallons and select your desired therapeutic concentration percentage. The calculator instantly returns the exact weight (grams) or volume (teaspoons) of salt required for your specific tank.
Use the result to measure salt accurately with a kitchen scale or measuring spoon, dissolve it in tank water before adding, and monitor fish behavior daily. Reduce salt levels gradually through 25% water changes every 3-7 days depending on the condition being treated.
Therapeutic Salt Dosage by Aquarium Volume
Use this reference table to verify calculator results for common aquarium sizes.
| Tank Volume (Gallons) | 0.1% Concentration (TSP) | 0.2% Concentration (TSP) | 0.3% Concentration (TSP) |
|---|---|---|---|
| 10 | 1/3 | 2/3 | 1 |
| 20 | 2/3 | 1.3 | 2 |
| 30 | 1 | 2 | 3 |
| 50 | 1.7 | 3.3 | 5 |
| 75 | 2.5 | 5 | 7.5 |
| 100 | 3.3 | 6.7 | 10 |
Measurements in teaspoons (TSP). 1 teaspoon aquarium salt ≈ 6 grams. Verify exact salt density with product labeling.
Common Fish Conditions and Recommended Salt Dosage
Different ailments benefit from varying salt concentrations and treatment durations.
| Condition | Recommended Concentration | Duration | Water Change Rate |
|---|---|---|---|
| Ich/White Spot | 0.2-0.3% | 7-14 days | 25% every 3 days |
| Fin Rot | 0.2% | 10-14 days | 25% weekly |
| General Stress Relief | 0.1-0.2% | 5-7 days | 25% weekly |
| Velvet Disease | 0.3% | 14-21 days | 25% every 2 days |
| Gill Fluke Treatment | 0.2-0.3% | 7-14 days | 25% every 3 days |
Always monitor fish behavior and remove carbon if using. Gradually reduce salt through partial water changes rather than abrupt removal.
Pro Tips
- Always dissolve salt in a separate container of tank water before adding to avoid shocking fish with concentrated solution.
- Remove activated carbon filters during salt treatment, as they absorb salt and reduce therapeutic effectiveness.
- Use a hydrometer or refractometer to verify salt concentration if treating high-value fish or for extended therapy periods.
- Maintain adequate aeration during salt treatment because elevated salinity reduces oxygen saturation in water.
Common Mistakes to Avoid
Using Iodized or Anti-Caking Salt
Table salt and kosher salt contain additives harmful to fish; always use non-iodized aquarium salt or marine salt for therapeutic dosing.
Ignoring Tank Substrate and Décor Volume
Failing to subtract 10-15% for gravel, plants, and decorations leads to overdosing; measure effective water volume, not just tank dimensions.
Maintaining Therapeutic Salt Indefinitely
Long-term salt exposure stresses fish kidneys and kills beneficial bacteria; always taper salt levels through water changes after 7-14 days of treatment.
Calculating Dosage Without Verifying Tank Volume
Using manufacturer-stated capacity instead of actual water volume causes serious miscalculations; always measure your tank with a measuring cup or formula.
Frequently Asked Questions
What is the ideal therapeutic salt concentration for freshwater aquariums?
The standard therapeutic dosage is 1-3 teaspoons per gallon, which creates a concentration of approximately 0.1-0.3%. Most treatments target 0.2% (2-3 ppm) for stress relief and parasite control.
How do I calculate salt dosage for an irregularly shaped aquarium?
Measure the length, width, and average depth in inches, multiply them together, divide by 231 to get gallons, then use this volume in the calculator. For non-rectangular tanks, estimate the effective volume by treating curves as partial sections.
Can I use table salt or kosher salt for therapeutic aquarium dosing?
No—use only aquarium salt or marine salt without additives like iodine or anti-caking agents. Table salt and kosher salt contain chemicals that harm fish gills and water chemistry.
How long should I maintain therapeutic salt levels in the aquarium?
Therapeutic dosing typically lasts 7-14 days for acute conditions like ich or fin rot. Gradual water changes reduce salt levels by 25% weekly after treatment begins.
What aquarium types require adjusted salt calculations?
Saltwater and brackish tanks need different dosing than freshwater systems. The calculator is designed for freshwater therapeutic use; marine systems already contain dissolved salts at 1.020-1.025 specific gravity.
How do I account for substrate and décor displacement in volume calculations?
Subtract 10-15% from total tank volume to account for gravel, rocks, plants, and decorations, then enter the adjusted volume into the calculator for accurate dosing.
What happens if I overdose aquarium salt therapeutically?
Overdosing above 0.5% can stress fish kidneys, damage plants, and disrupt beneficial bacteria. Always verify your tank volume before calculating to prevent accidental overdosing.
References & Resources
Last updated: April 2026
- American Aquarium Products - Salt Treatment Guidelines
Comprehensive guide to therapeutic salt dosing for freshwater fish conditions and treatment protocols.
- University of Florida IFAS - Fish Disease Management
Research-backed recommendations for salt therapy in aquaculture and home aquariums with dosage specifications.
- The Spruce Pets - Aquarium Salt for Fish Health
Practical guide explaining therapeutic salt concentrations, application methods, and safety considerations for freshwater systems.
- Aquatic Community - Salt Treatment Safety Data
Details on salt concentrations for specific fish diseases, duration guidelines, and compatibility with tank inhabitants.