Aquarium Salt Calculator

About the Aquarium Salt Calculator

The Aquarium Salt Calculator determines the correct amount of aquarium salt (NaCl) to add for freshwater fish treatments, brackish water setups, and marine aquarium salinity. Enter your tank volume, desired salinity or treatment concentration, and get precise dosing in teaspoons, tablespoons, cups, and grams. That lets you match the dose to the tank size before you mix anything.

Aquarium salt is one of the most versatile and affordable medications for freshwater fish. Low concentrations (1 tsp/gal) reduce stress and boost slime coat production. Medium concentrations (1 tbsp/gal) treat ich, velvet, and fungal infections. Higher concentrations (up to 3 tbsp/gal) serve as salt dips for parasites.

The calculator handles freshwater treatment dosing, brackish water salinity preparation, and marine aquarium specific gravity. It accounts for water already in the tank (partial water changes), shows dosing schedules for gradual salt addition, and provides compatibility warnings for salt-sensitive species. That makes it easier to convert a target concentration into a practical dose without switching between unit systems by hand.

When This Page Helps

Use this calculator when you need to translate tank volume into an actual salt dose instead of estimating by eye. It is useful for freshwater treatment dosing, brackish setup planning, and checking how much salt to replace after a partial water change. That helps keep the salinity change controlled instead of guesswork.

How to Use the Inputs

1. Enter your tank volume in gallons or liters.
2. Select the purpose: treatment, brackish, or marine.
3. Choose a treatment level or enter a custom concentration.
4. View the salt quantity needed in multiple units.
5. Follow the dosing schedule for gradual addition.
6. Check species compatibility before adding salt.

Example Calculation

Tips & Best Practices

• Always dissolve salt in a cup of tank water before adding — never pour dry salt directly into the tank.
• Increase salt concentration gradually over 24-48 hours to prevent osmotic shock.
• Salt does not treat bacterial infections — use appropriate antibiotics for those.
• If treating with salt and heat (for ich), raise temperature to 86°F and use 1 tsp/gal for 10 days.
• Keep a refractometer ($15-30) for accurate salinity measurement in brackish and marine tanks.

How Salt Treats Fish Disease

Salt disrupts the osmotic balance of freshwater parasites and fungi, which are adapted to low-salinity environments. At concentrations fish can tolerate, parasites dehydrate and die. Salt also stimulates the fish's slime coat production — their first line of defense against pathogens.

The most common use is treating Ichthyophthirius (ich/white spot disease). Salt combined with elevated temperature (86°F) kills ich in its free-swimming stage. The salt makes the treatment more effective and reduces the infection cycle from 2 weeks to 3-5 days.

Salt Dip Protocol

Salt dips are short-term (5-30 minute) immersions in high-concentration salt water (4 tablespoons per gallon). Used to treat external parasites like flukes and anchor worms. Always observe the fish — if it rolls over or shows extreme distress, return it to the main tank immediately. Prepare an aerated container at the same temperature as the main tank.

Brackish Water Aquariums

Brackish species (figure-eight puffers, bumblebee gobies, mollies) thrive in controlled salinity between freshwater and marine. Use marine salt mix (not aquarium salt) for brackish setups because it contains essential trace minerals. Measure with a hydrometer or refractometer, not by taste or volume.

Frequently Asked Questions

• How much salt per gallon for freshwater fish?

  Stress reduction / prevention: 1 tsp per gallon. Mild treatment (ich, fin rot): 1 tbsp per gallon. Strong treatment (parasites): 2-3 tbsp per gallon. Salt dip (short-term): 4 tbsp per gallon for 5-30 minutes.

• Is aquarium salt the same as table salt?

  Aquarium salt is pure NaCl without additives. Table salt may contain iodine, anti-caking agents, and flow agents that can harm fish. Use only aquarium salt, rock salt, or solar salt (pure, non-iodized).

• Which fish cannot tolerate salt?

  Salt-sensitive species: Corydoras catfish, most tetras, otocinclus, bristlenose plecos, shrimp, and most live plants. These species tolerate only low concentrations (0.5 tsp/gal maximum). Remove them before stronger treatments.

• How long should salt treatment last?

  Typical treatment: 10-14 days. Maintain the salt level during treatment — salt does not evaporate, only leaves through water changes. After treatment, remove salt gradually via water changes over 3-5 days.

• Does salt evaporate from aquariums?

  No. When water evaporates, salt stays behind. Only top up evaporation with fresh (unsalted) water. Only add salt when doing a water change, proportional to the water removed.

• What is the salinity for brackish water?

  Brackish water: 1.003-1.015 specific gravity (5-20 g/L). Low brackish (mollies): SG 1.003-1.005. Mid brackish (puffers): SG 1.005-1.010. High brackish (scats, monos): SG 1.010-1.015. Marine: SG 1.020-1.025 (33-35 g/L).