Aquarium Salt Calculator — Freshwater Dosage & Dip Guide
Calculate exact aquarium salt dosages in tablespoons, teaspoons, and grams for stress reduction, nitrite protection, parasite treatment, or bath dips.
Salt Parameters & Water Volume
Recommended Salt Dosage
- Never dump dry salt crystals directly into the aquarium. Undissolved crystals sink and burn bottom-dwelling fish or snails.
- Scoop 1–2 quarts of tank water into a clean pitcher and stir until the salt completely dissolves.
- Pour one-third of the dissolved solution into a high-flow area (near filter outflow).
- Wait 2 hours, then add the second third. Add the final third 2 hours later. This gradual introduction eliminates osmotic stress.
Standard Aquarium Salt Dosage Sizing Matrix
Complete salt dosage reference across 10 standard tank sizes in Tablespoons, Teaspoons, and Grams.
| Tank Size (Gal / L) | Level 1 Tonic (Stress) | Level 2 Shield (Nitrite) | Level 3 Ich / Parasites | In Grams (Level 1 / 3) |
|---|---|---|---|---|
| 5 Gallon (19 L) Nano | 1.0 tbsp (3 tsp) | 2.0 tbsp (6 tsp) | 5.0 tbsp (15 tsp) | 15 g / 75 g |
| 10 Gallon (38 L) Standard | 2.0 tbsp (6 tsp) | 4.0 tbsp (12 tsp) | 10.0 tbsp (30 tsp) | 30 g / 150 g |
| 20 Gallon Long (75 L) | 4.0 tbsp (12 tsp) | 8.0 tbsp (24 tsp) | 20.0 tbsp (1.25 cups) | 60 g / 300 g |
| 29 Gallon (110 L) Standard | 5.8 tbsp (17 tsp) | 11.6 tbsp (35 tsp) | 29.0 tbsp (1.8 cups) | 87 g / 435 g |
| 40 Gallon Breeder (150 L) | 8.0 tbsp (0.5 cup) | 16.0 tbsp (1.0 cup) | 40.0 tbsp (2.5 cups) | 120 g / 600 g |
| 55 Gallon (208 L) Standard | 11.0 tbsp (0.7 cup) | 22.0 tbsp (1.4 cups) | 55.0 tbsp (3.4 cups) | 165 g / 825 g |
| 75 Gallon (284 L) Standard | 15.0 tbsp (0.9 cup) | 30.0 tbsp (1.9 cups) | 75.0 tbsp (4.7 cups) | 225 g / 1,125 g |
| 90 Gallon (340 L) Standard | 18.0 tbsp (1.1 cups) | 36.0 tbsp (2.25 cups) | 90.0 tbsp (5.6 cups) | 270 g / 1,350 g |
| 125 Gallon (473 L) Large | 25.0 tbsp (1.5 cups) | 50.0 tbsp (3.1 cups) | 125.0 tbsp (7.8 cups) | 375 g / 1,875 g |
| 150 Gallon (568 L) Show | 30.0 tbsp (1.9 cups) | 60.0 tbsp (3.75 cups) | 150.0 tbsp (9.4 cups) | 450 g / 2,250 g |
Aquarium Salt Guide: How Salt Promotes Fish Health & Treats Disease.
Aquarium salt (sodium chloride, NaCl) is one of the oldest, safest, and most versatile aquatic medications. By temporarily altering water salinity, salt promotes natural fish osmoregulation, thickens protective slime coats, blocks lethal nitrite toxicity, and eradicates microscopic protozoan parasites like Ich without killing biological filter bacteria.
Osmoregulation & Stress Relief
Freshwater fish maintain internal bodily salinity around 9.0 ppt (parts per thousand). Because pure freshwater surrounds them, water constantly rushes into their bodies via osmosis. Sick or stressed fish expend massive metabolic energy pumping water out through their kidneys. Adding Level 1 aquarium salt lowers this osmotic differential, giving recovering fish vital energy to heal.
Nitrite Toxicity Shield
Nitrite (NO₂⁻) is absorbed through fish gills via chloride cells, converting blood hemoglobin into methemoglobin (brown blood disease), which cannot carry oxygen. Chloride ions (Cl⁻) from dissolved aquarium salt outcompete nitrite molecules for absorption sites at the gills, completely preventing nitrite poisoning during new tank cycling emergencies.
Ich (White Spot) Eradication
At Level 3 (1 tbsp per gallon / 4 g/L), salt increases osmotic pressure beyond what single-celled protozoan parasites (like Ichthyophthirius multifiliis) can withstand. When paired with gradually raised temperatures (86°F / 30°C), the parasite's developmental lifecycle speeds up and free-swimming theronts are rapidly dehydrated and destroyed.
Aquarium Salt vs. Epsom Salt: Which Should You Use?
Aquarium salt is Sodium Chloride (NaCl), used for external parasites, slime coat stimulation, and gill protection. Epsom Salt is Magnesium Sulfate (MgSO₄ · 7H₂O), which acts as a gentle laxative and fluid-drawing agent. If your fish suffers from dropsy (pineconing scales), severe constipation, or swim bladder bloating, use Epsom salt at 1 teaspoon per gallon rather than sodium chloride.
Frequently Asked Questions
Expert answers to detailed planning questions for this calculator module.
Aquarium Salt & Treatments
How much aquarium salt do I add per gallon of water?
Dosage depends on your treatment goal: For general stress reduction and electrolyte support (Level 1), use 1 tablespoon per 5 gallons (1.5 g/L). For mild fungal infections, fin rot, and nitrite poisoning protection (Level 2), use 1 tablespoon per 2.5 gallons (2.5 g/L). For severe external parasites like Ich (Level 3), use 1 tablespoon per 1 gallon (4.0 g/L). Always dissolve salt in a container of aquarium water before adding it gradually over several hours.
Does aquarium salt evaporate when tank water evaporates?
No, salt NEVER evaporates. Only pure water evaporates into the air, leaving all dissolved salt behind. If you top off an aquarium due to evaporation, add PURE fresh water with zero salt. You should only add replacement salt during physical water changes, dosing exclusively for the volume of new replacement water being added.
How do I treat Ich (White Spot Disease) with aquarium salt?
To treat Ich effectively: Dose aquarium salt to Level 3 (1 tablespoon per gallon / 4 g/L) over 24 to 48 hours. Simultaneously raise water temperature gradually to 86°F (30°C) if your fish tolerate it, which stops the parasite's life cycle. Maintain intense aeration with air stones because warm, salty water holds less dissolved oxygen. Continue treatment for a minimum of 10 to 14 days to eradicate all free-swimming theronts.
Are Corydoras, Plecos, and live plants safe with aquarium salt?
Caution is required. Scaleless fish (Corydoras, loaches, knife fish) and catfish have heightened sodium sensitivity — start with a half dose (maximum 1 tablespoon per 10 gallons) and monitor closely. Live aquatic plants (especially Hornwort, Anacharis, and Vallisneria) melt rapidly at salt concentrations exceeding Level 1. Freshwater snails and delicate shrimp are also intolerant of sustained salt treatment.
Can I use kitchen table salt or Epsom salt instead of aquarium salt?
Do not use iodized table salt with anti-caking agents (like yellow prussiate of soda), as these additives are toxic to fish. Pure, non-iodized coarse kosher salt or canning salt is chemically identical to aquarium salt (pure NaCl). Epsom salt (magnesium sulfate, MgSO4) is chemically distinct and is used for relieving dropsy, swim bladder bloating, and severe constipation, not for parasite eradication.