How Much Salt for a Salt Bath: 0.5% Is 5 g per Liter, with Steps for Goldfish and Medaka

Salt = water volume (L) × strength (%) × 10 grams

One liter of water weighs about 1,000 g, so a 0.5% solution needs 1,000 × 0.005 = 5 g of salt. That means the grams of salt come from water volume (L) × strength (%) × 10. A 10 L bucket takes 10 × 0.5 × 10 = 50 g, and a 60 cm standard tank (about 51.5 L of actual water) takes about 258 g.

0.3% is often used for acclimation and prevention, 0.5% is the standard salt bath, and 0.6% is used for problems such as white spot in goldfish. Stronger doesn't mean more effective, and close to 1% puts a heavy strain on fish. If it's your first time, stick to 0.5%.

Measuring with teaspoons and tablespoons when you have no scale

Refined salt (free-flowing table salt) is about 6 g per teaspoon and about 18 g per tablespoon. Coarse salt has more gaps between grains and holds some moisture, so it's lighter at about 5 g per teaspoon.

• Salts you can use: table salt, refined salt, coarse salt, natural salt and others that are mainly sodium chloride
• Salts to avoid: seasoned salts with flavor enhancers or herbs, salts with added bittern, and salts with anti-caking agents
• Marine salt mix for saltwater fish has a different composition, so don't use it for a freshwater salt bath
• Dissolve the salt fully in bucket water before adding it. Added as grains, it creates concentrated patches on the bottom

How to give goldfish and medaka a salt bath

1. 1

   Prepare a separate container

   Don't salt a tank with aquatic plants, shrimp or snails; move only the sick fish to a bucket or plastic tub. Measure the container's water volume and calculate the salt.

2. 2

   Match the temperature, then move the fish

   Use water from the original tank, or water at the same temperature. Keep the difference within 1–2 °C before moving them.

3. 3

   Dissolve and add the salt in about 3 doses

   Going to 0.5% in one step shocks the fish, so add it in about 3 doses a few hours apart. For 10 L, that's about 17 g each.

4. 4

   Hold back on food and watch

   During the bath, stop feeding or give very little. Leftover food fouls the water and makes the bath less effective. About 1 week is the usual length.

5. 5

   Change water with salt water of the same strength

   If you change water partway, dissolve the same strength of salt in the new water. To replace 3 L out of 10 L, put 15 g in the new 3 L.

Once the fish recover, don't return them to fresh water abruptly; dilute the salt by changing a little water at a time over several days. For example, replacing one-third with fresh water each day brings the strength down to about 30% in around 3 days. Then acclimate the fish and return them to the original tank.

Salting a whole tank, and adding salt at water changes

If a tank holds only goldfish or only medaka, with no plants or shrimp, you may treat the whole tank. Here too, calculate from the actual water and add it in about 3 doses. With 4 cm of Oiso sand and the water surface 3 cm below the rim, the amounts for 0.5% are as follows.

When changing water, calculate the salt from the new water only. The water left in the tank already has salt dissolved in it, so dosing for the whole tank again makes it too strong. When the level falls through evaporation, top up with fresh water, since salt doesn't evaporate.

Animals unsuited to salt baths, and when to stop

• Aquatic plants: many wither or melt in 0.5% salt water
• Shrimp and snails: cherry shrimp, Amano shrimp and mud snails are sensitive to salt
• Catfish such as corydoras and plecos, and loaches, are considered sensitive, so lower the strength or avoid it
• Filter bacteria: salting the main tank can reduce the filter's effectiveness
• When using fish medication, check its instructions to see whether it can be combined with salt

A salt bath reduces the difference between the salt in a fish's body and in the water, limiting the drain on its strength. It isn't a medicine that cures the disease itself, so if there's no improvement after about a week, or white spots or cottony growths are increasing, consider a fish medication that matches the symptoms.

For white spot in goldfish, some people also raise the water temperature slowly alongside the salt bath. For choosing a heater with an adjustable temperature, see Choosing Heater Wattage and Filter Flow.

FAQ

How many grams of salt do I need for a 0.5% salt bath?

5 g per liter of water. That's 10 g for 2 L, 50 g for 10 L and 100 g for 20 L. You can calculate it as water volume (L) × strength (%) × 10.

How many teaspoons of salt is a salt bath?

Refined salt is about 6 g per teaspoon, so the 50 g needed for 10 L at 0.5% is about 8.3 teaspoons, or about 2.8 tablespoons. Coarse salt is lighter at about 5 g per teaspoon.

How many days should a salt bath last?

About 1 week. Once the fish recover, gradually replace the water with fresh water over several days to dilute the salt, then return them to the original tank. If they don't improve in about a week, consider a medication that matches the symptoms.

Can medaka have a salt bath too?

Yes. As with goldfish, 0.5% is the standard. But if cherry shrimp or aquatic plants share their container, move the medaka alone to a separate container for the bath.