How much salt to add to a pond
Salt levels in ponds are given in percent. The sum is simple:
In US units, 0.1% is about 0.83 lb for every 100 gallons, and 0.3% is 2.5 lb for every 100 gallons.
| Salt level | For every 1,000 liters | For every 100 US gallons | Used for |
|---|---|---|---|
| 0.1% | 1 kg | 0.83 lb | A low, general level |
| 0.3% | 3 kg | 2.5 lb | Treatment |
| 0.5% | 5 kg | 4.2 lb | Sick fish, in a separate tank |
Worked example. A 1,000 gallon pond (3,785 liters), to be raised to 0.3%.
3,785 × 3 grams = 11,356 grams = 11.4 kg, or 25 lb. Spread over 3 days, that is about 8.3 lb a day.
You will often see "1 pound per 100 gallons" given for 0.1%. That is slightly generous: 1 lb in 100 gallons is 0.12%.
Which level to use
- 0.1% is the level Aquascape gives for regular use, and the most that many pond plants will take.
- 0.3% is the usual treatment level. University of Florida Extension gives 0.1 to 0.3% as the range that eases stress on fish.
- Above 0.3% is for sick fish and is better done in a separate tank. Above 0.5% salt itself becomes harmful.
Salt is not a cure for everything, and not every pond needs it. If your fish are ill, find out what is wrong first.
Add it slowly
Raise the level in steps: a third each day for three days is the usual advice. Dissolve the salt in a bucket of pond water before it goes in. Never tip dry salt onto fish or plants.
Use plain salt with nothing added: pond salt or non-iodized salt.
Measure before you add
Salt does not evaporate and filters do not remove it. It only leaves with water you take out. If you dose again without measuring, the level climbs each time, and fish have been killed that way.
Read the level with a salt meter, enter it under "Salt already in the pond", and the calculator works out only what is missing.
To bring the level down, change water: replacing a quarter of the water removes a quarter of the salt.
Common mistakes
- Adding a second dose without measuring. The first dose is still in the water.
- Guessing the pond volume high. Too much salt is far worse than too little.
- Pouring dry salt straight in. It can burn fish and plants where it lands.
- Using iodized table salt. Use plain, non-iodized salt.
- Leaving plants in at treatment level. Many are harmed above 0.1%.
Questions and answers
How much salt do I add to my pond?
For 0.1%, add 1 kg for every 1,000 liters, or 0.83 lb for every 100 US gallons. For 0.3%, three times that: 3 kg per 1,000 liters or 2.5 lb per 100 gallons.
How much salt for a 1,000 gallon koi pond?
About 8.3 lb (3.8 kg) for 0.1% and 25 lb (11.4 kg) for 0.3%. Spread a 0.3% dose over three days.
Is 1 pound of salt per 100 gallons 0.1%?
Nearly. One pound in 100 US gallons is 0.12%. A true 0.1% is 0.83 lb per 100 gallons.
Will salt hurt my pond plants?
Many pond plants are harmed above 0.1%. Take them out before raising the salt to treatment level, or keep to 0.1%.
How do I lower the salt level in a pond?
Only by changing water. Salt does not evaporate, so replacing a quarter of the water removes a quarter of the salt.
Numbers for standard tanks
Have a standard tank? Its size, weight, heater and stocking are already worked out.
- 10 gallon tank
- 20 gallon long tank
- 29 gallon tank
- 40 gallon breeder tank
- 55 gallon tank
- 75 gallon tank
- 125 gallon tank
- All tank sizes
Sources
- Aquascape, "Is salt good for a koi pond?": 1 kg per 1,000 L is about 0.1%; 0.3% and up for treatment; check the level before adding
- Koi Club of San Diego, "The bottom line on salt use in ponds": 0.3% as the treatment level, reached over 3 days; no more than 0.1% with plants
- University of Florida IFAS Extension, "The use of salt in aquaculture" (VM007): 0.1 to 0.3 percent to ease stress on fish