Quick answer: Use aquarium salt only as a short freshwater aid. Follow the maker dose, usually 1 tablespoon per 5 gallons. Skip a daily dose in planted tanks, and never swap it for marine salt.
Aquarium salt is sodium chloride for freshwater tanks, and common U.S. labels list 1 tablespoon per 5 gallons. This page is a label comparison of four freshwater salts and one marine mix; we did not run tank trials or diagnose sick fish.
Selection rule: We included U.S. freshwater sodium-chloride salts with a live maker page, plus Instant Ocean Sea Salt as a contrast mix. We left out Epsom salt, iodized table salt, and cichlid mineral blends.
What aquarium salt is
Aquarium salt is a freshwater sodium-chloride product, not a copy of ocean water.
API Fishcare’s page for API Aquarium Salt says the product is made from evaporated sea water. The DailyMed listing for that same Mars Fishcare North America product lists sodium chloride at 100 grams in 100 grams. Fritz Aquatics’ page for Fritz A+ Aquarium Salt also names sodium chloride as the active ingredient.
That chemistry is simple, and it is not a marine salt mix. Instant Ocean’s page for Instant Ocean Sea Salt uses 1.5 pounds of product to make 5 gallons of saltwater. That mix targets a specific gravity of 1.022.
Tetra’s page for Tetra Aquarium Salt, product number 78740, limits the 16-ounce bag to freshwater tanks. The same page says the product is not for food fish.
Use this Three-Bucket Salt Rule when you shop:
- Bucket 1: freshwater aquarium salt, sodium chloride only
- Bucket 2: a short, labeled salt bath in a separate container
- Bucket 3: a marine mix, used only to make saltwater
Keep a bucket-3 bag off a standard freshwater community tank.
When to use it
Use aquarium salt when a maker label names a short job, not as a forever additive.
API Fishcare tells owners to use API Aquarium Salt at setup, at a water change, or when treating fish disease. The same page says the salt does not evaporate and is not filtered out, so you add it only with each water change.
Fritz Aquatics uses a similar window for Fritz A+ Aquarium Salt. Add it to reduce stress during a new setup and water changes, or when a specific health issue is being solved. That page also lists constipation, fluid retention, and mild swim bladder trouble as labeled uses.
Tetra’s page lists several jobs for the 16-ounce bag:
- Condition water and reduce stress at 1 level tablespoon per 10 gallons
- Introduce new fish at 1 tablespoon per 5 gallons
- Clean glass and accessories with 6 tablespoons in 1 quart of water
- Hatch brine shrimp eggs using the dose on the egg pack
Jungle Labs’ page for Jungle Aquarium Salt, SKU NJ007, lists stress reduction, electrolytes, cleaning, and brine-shrimp hatching. That page says to add the salt with every water change. It does not print a tablespoon-per-gallon number.
Our research team analyzed those published uses and did not watch live treatments. A label can name a use and still be a poor fit for plants or shrimp.
Do not use freshwater aquarium salt as a pH tool. If you need a higher pH, use a method built for that job in our guide on how to raise pH in an aquarium.
How much to add
Dose only the water you are treating, and only at the number on that product’s page.
API Fishcare’s instructions are the most common U.S. freshwater dose:
- 1 rounded tablespoon for every 5 U.S. gallons (20 liters)
- 1/2 rounded teaspoon for every U.S. gallon (4 liters)
The DailyMed label for API Aquarium Salt repeats that same pair of measures. It states that the 16-ounce (454-gram) carton treats up to 107 U.S. gallons (404 liters) of fresh water.
DailyMed lists carton weights of 454 grams, 936 grams, 1,843 grams, and 22,680 grams. API Fishcare lists retail sizes of 16 ounces, 33 ounces, 65 ounces, and 50 pounds.
Tetra’s conditioning dose is lower than API’s tonic dose. Tetra’s page says 1 level tablespoon per 10 gallons for conditioning, and 1/4 teaspoon per gallon for goldfish bowls.
Fritz Aquatics splits community tanks from livebearers:
- Tropical community and goldfish tanks: 1 tablespoon per 5 gallons
- Livebearer tanks: up to 1 tablespoon per gallon, raised over 3 to 4 days
- External-parasite bath: a 2.5% saline bath using 1/2 cup (95 grams) per 1 gallon
- Bath time: 15 to 30 minutes, then return the fish to freshwater
- Cleaning mix: 1/3 cup of salt in 1 gallon of warm water
Fritz Aquatics lists three bag sizes: 1 pound (454 grams), 2 pounds (907 grams), and 50 pounds (22.7 kilograms).
Work through a water change with the API number:
- Measure only the gallons you are removing.
- Dissolve the matching salt dose in a bucket of treated water.
- Add that water after the old water is out.
- Do not add a full-tank dose on top of salt that is still in the tank.
API Fishcare’s page is plain on that last point. Salt stays in the water, and filters do not pull it out.
Freshwater salt products compared
The table below compares published attributes, not a ranked list and not a price ladder.
Our research team compared maker pages for products that are currently sold. We recorded only attributes those pages print, and we did not invent missing doses.
| Product | Type on the maker page | Listed tank dose | Sizes on the maker page | Extra label note |
|---|---|---|---|---|
| API Aquarium Salt | Evaporated sea water; sodium chloride | 1 rounded Tbsp per 5 U.S. gal | 16 oz, 33 oz, 65 oz, 50 lb | Add only with water changes |
| Tetra Aquarium Salt (No. 78740) | Freshwater aquarium salt | 1 level Tbsp per 10 gal to condition; 1 Tbsp per 5 gal for new fish | 16 oz bag | Not for food fish |
| Fritz A+ Aquarium Salt | Sodium chloride | 1 Tbsp per 5 gal; livebearers up to 1 Tbsp per gal over 3–4 days | 1 lb, 2 lb, 50 lb | 2.5% bath: 1/2 cup (95 g) per gal for 15–30 min |
| Jungle Aquarium Salt (SKU NJ007) | Freshwater aquarium salt | No numeric tank dose on the maker page | No numeric size on the maker page | Add with every water change |
| Instant Ocean Sea Salt | Synthetic sea salt mix | 1/2 cup per U.S. gal; 1.5 lb makes 5 gal at SG 1.022 | Mixes for 25, 50, 160, and 200 gal | Recommended SG 1.020–1.024 at 77°F |
Read the Instant Ocean row as a warning, not a freshwater pick. Instant Ocean’s page also says to change 20% of marine aquarium water every two weeks.
Jungle Labs’ page names uses but does not give a tablespoon count. If you buy that bag, read the dose on the carton in your hand.
When not to use it
Skip aquarium salt when plants, sensitive fish, or the wrong salt type are in the tank.
API Fishcare’s page says some live plants may be sensitive, and Fritz Aquatics prints the same plant caution. Tetra’s page says the salt is safe for freshwater aquarium fish and plants, then adds that some plants may be sensitive.
Those three lines do not agree in tone, so treat plants as a reason to pause. If you keep a planted tank, start with plant choice, not a salt dose, in our guide to low-maintenance planted aquarium plants for beginners.
Tetra’s page names catfish and tetras as species that can be sensitive to salt. That is a maker warning, not a species encyclopedia. Check the fish you own before you dose the display tank.
Do not pour Instant Ocean Sea Salt into a freshwater tank as stronger aquarium salt. Instant Ocean’s page mixes 1/2 cup per U.S. gallon for small batches. That batch aims for a specific gravity of 1.020 to 1.024 at 77°F.
Do not use a display tank as a bath. Fritz Aquatics’ 2.5% bath uses 95 grams of salt in 1 gallon for 15 to 30 minutes. The page says to remove the fish at the first sign of stress.
Do not stack salt after every filter rinse. API Fishcare states that aquarium salt is not filtered out. A Top Fin aquarium filter EF-S still moves water and traps debris, but it does not reset the salt level.
How to add it without stacking the dose
Dissolve the salt first, then replace only the salt that left with the old water.
API Fishcare’s FAQ says to add 1 rounded tablespoon per 5 gallons, or 1/2 rounded teaspoon per gallon, when you change water. Put other treatments in the new water before the salt, according to that same FAQ.
A simple 20-gallon example using the API number:
- Full-tank tonic: 4 rounded tablespoons (20 divided by 5)
- After a 5-gallon change: 1 rounded tablespoon in the new 5 gallons
- After a 10-gallon change: 2 rounded tablespoons in the new 10 gallons
Do not add those 4 tablespoons again if the tank already holds a full dose.
Tetra’s cleaning mix is not a tank dose. Dissolve 6 tablespoons in 1 quart, soak or wipe, then rinse with fresh water. Fritz Aquatics’ cleaning mix is 1/3 cup in 1 gallon of warm water, and that soak stays out of the display tank.
For a labeled bath, use a hospital container:
- Match temperature to the display tank.
- Mix Fritz’s 1/2 cup (95 grams) per gallon if you are following that page.
- Watch the fish for the full 15 to 30 minutes.
- Move the fish back to freshwater at the first sign of stress.
Our research team analyzed those printed steps and did not time baths on live fish. If a fish is in clear distress, stop the bath.
Salt will not fix a broken cycle, a jammed filter, or a pH swing. Measure ammonia, nitrite, and pH first, then decide whether a label dose even applies.
FAQ
Is aquarium salt the same as marine salt?
No. Freshwater aquarium salt is sodium chloride, while Instant Ocean Sea Salt is a synthetic sea salt mix. Instant Ocean’s page uses 1.5 pounds of mix to make 5 gallons at a specific gravity of 1.022.
How much aquarium salt should I add per gallon?
API Fishcare’s page lists 1/2 rounded teaspoon per U.S. gallon, or 1 rounded tablespoon per 5 gallons. Tetra’s page lists 1/4 teaspoon per gallon for goldfish bowls. Use the number on the bag you bought.
Does aquarium salt evaporate or get filtered out?
API Fishcare’s page says aquarium salt does not evaporate and is not filtered out. Fritz Aquatics prints the same note. Add salt only for the gallons you replace.
Can I use aquarium salt in a planted tank?
API Fishcare and Fritz Aquatics both warn that some live plants may be sensitive. Tetra’s page also says some plants may be sensitive. Skip a standing salt dose in a planted display tank unless the plant list and the label both support it.
How much water does a 16-ounce carton of API Aquarium Salt treat?
The DailyMed listing for API Aquarium Salt says the 16-ounce (454-gram) carton treats up to 107 U.S. gallons (404 liters). That figure matches a full-tank dose at the label rate, not a marine mix rate.
Can I use Instant Ocean in a freshwater community tank?
Not as a substitute for aquarium salt. Instant Ocean’s page is a seawater recipe of 1/2 cup per U.S. gallon for small batches. That load sits far above a 1-tablespoon-per-5-gallon freshwater tonic.
Should I keep salt in the tank all the time?
API Fishcare’s page limits use to setup, water changes, and disease treatment. Fritz Aquatics limits use to stress reduction during setup and water changes, or to a named health issue. Those freshwater labels point to short, measured use, not a permanent brackish tank.
