Whether to add salt to your koi pond or create salt dips for sick, injured, or stressed fish is a debated topic among hobbyists. The sweet side of salt is that it can increase antibody protection, combat waterborne pathogens, and improve oxygen intake.
However, when overused or applied incorrectly, salt can create more problems than it solves. Here, we will review the pros and cons of adding salt to treat the entire population in your pond, as well as crafting salt dips for specific sick, injured, or stressed fish.
How Salt Works
Though koi are freshwater fish, their bodies still require salt. The typical salinity level for a freshwater pond is about 0.05%. Koi have a blood salinity of approximately 0.9%, which maintains a healthy balance of electrolytes. If a koi’s internal salinity levels drop, it needs to expend significant energy to replenish the loss.
Adding salt to your pond causes the external salinity of the pond to exceed the fish’s internal salinity, which decreases the water entering through the mouth and gills so that the koi’s body has less to process. This is helpful when koi need to preserve strength to fight injury or illness or to calm down when agitated.
Non-iodized sodium chloride is the best type of salt to use in ponds with koi and goldfish. Never use salt with fluoride or iodine–which includes table salt–as this can harm and possibly kill your fish. Avoid water softener salts or other types that contain additives such as Yellow Prussiate of Soda (YPS), a toxic anti-caking ingredient. Fish-friendly pond salt is made from pure evaporated sea salt and nothing else.
Symptoms of Distress
If your koi gets sick, it’s important to quickly identify and treat the problem before it worsens and spreads to other fish. Some signs that a koi is in distress include:
- Discoloration
- Slow movement
- Clamped fins
- Lethargy (lying down or staying in the same place)
- Rapid gill movement
- Raised, loose, or missing scales
- Loss of fin transparency or visible fin rot
- Sunken eyes
- Skin bulges
- Lesions
- Erratic swimming
Although many potential benefits of salt exist, adding it to your pond should either serve as an intervention or a preventative for a foreseeable issue. If everything in your pond is going swimmingly, spare the sodium. Salt baths are not a cure-all nor a long-term solution. However, salt can be an effective first response.
Adding Salt to Your Pond
The recommended salinity for most health benefits for koi is between 0.3% and 0.6%. It’s better to start on the lower end, which you can achieve by adding 3 pounds of salt per every 100 gallons of water. Measure salinity with a battery-operated digital reader, a quick and accurate device available online and in garden supply stores.
Whenever salt is used, it should be dissolved in a bucket of pond water first, as undissolved salt can irritate or burn gills and skin. Test the water quality of your pond after adding salt, as fish tend to excrete high amounts of ammonia during exposure to it.
Pond Salt Pros
✔️Puts the Pause on Parasites. A pond salt treatment will help clear a variety of parasites, typically within 14 to 21 days. The increased salinity within the pond draws water from the parasite, causing it to dehydrate very quickly. Most protozoan parasites easily fall victim to salt, including chilodonella, as well as flukes and other ectoparasites.
✔️ Banishes Bacteria. Salt kills most bacteria in the same way as parasites, essentially sucking the water from them until they dry out. Without water, bacterial proteins cannot function, and the cell collapses. Salt works efficiently on columnaris bacteria.
✔️ Stimulates Slime. Because salt is a mild irritant, the koi’s body responds by producing a thicker slime coat. The slime coat is a mucous membrane that provides an outside layer of protection against deadly Aeromonas/pseudomonas and other toxins in your pond. It also plays an important role in a koi’s immune system and streamlines your fish’s swimming.
✔️Assists Osmosis. When fish experience acute stress from injury, disease, handling, or transport, they release hormones and neurotransmitters that accelerate breathing, causing them to overhydrate and lose salt. Adding salt to the koi’s habitat can alleviate this osmotic imbalance. Additionally, higher salt content helps with the osmoregulation function of the gills. The koi will not have to work as hard to get water back out of its body, which is helpful for a stressed koi or one with excess mucus on the gills.
✔️Soothes Stress. Elevated sodium levels within the koi’s body temporarily dull the autonomic nervous system’s natural response to stress by inhibiting hormones that anxiety would otherwise activate. This makes salt a potential tool to help new fish stay calm as they acclimate to a new environment.
✔️ Combats Cold. Falling temperatures slow koi’s metabolism and natural salt production, and their organs begin to work less efficiently. Using a small amount of salt can replenish their sodium levels, easing the winter transition and helping them preserve energy for the spring.
✔️ Enhances Electrolytes. Salt adds electrolytes to the water, which benefits several organs, including the eyes, heart, and kidneys.
✔️ Nitrite Neutralizer. Salt can mitigate the symptoms of nitrite poisoning. Nitrites prevent a koi’s red blood cells from absorbing oxygen. This can lead to the development of brown blood disease (resulting from the combination of hemoglobin and nitrite), which will suffocate koi internally. Salt helps fight nitrite toxicity by decreasing the amount of nitrite-laden water the koi can take in.
✔️ Helpful Healer. Pond salt can help to cleanse wounds and promote healing. Your koi are most prone to injury during the spawning season, so this is a good time to add salt as a preventative to keep injuries from becoming infected.
Pond Salt Cons
While some enthusiasts rave about the benefits of adding salt, others caution against it. Ultimately, what starts as helpful can quickly become harmful if used too freely or for too long.
❌ A Pain to Drain. Salt will not evaporate from your pond water, and your filtration systems will not remove it. You will need to remove the salt yourself after the treatment period via frequent partial water changes. If you’re sticking with salt, only add back the amount lost through the water removed, or you will have far too much.
❌ Herbicidal Maniac. Pond salt will kill plants, so if you rely on a robust biological filtration system or enjoy the ambiance that decorative water plants provide, you will have to go easy on the salt. Salinity levels below 0.3% are generally safe for most pond plants, though keeping it below this mark will void some of the benefits for your koi. When adding salt to your pond, avoid direct contact with plants.
❌ Chemical Confounder. Do not add salt to your pond if you are using other chemical water treatments. Sodium chloride is not compatible with most of them, and mixing chemicals can cause a reaction that kills all your fish. If you have already added salt and need to apply a stronger chemical, you will have to drain and refill your pond first.
❌ Not Rare to Need Repair. Because salt is corrosive, it can erode metallic features around your pond. It can also kill beneficial bacteria inside your mechanical filter, though it won’t harm its function.
❌ Overdose Alert. If you are adding salt to your pond, it is imperative that you monitor the salinity levels regularly and make additions gradually. Prolonged exposure to salinity levels above 0.6% can quickly make your fish sick and will ultimately become fatal.
❌ Resilient Resistance. Pathogens can build resistance when salt concentrations remain high for an extended period, rendering this intervention ineffective. A number of salt-resistant parasites have emerged in ponds (including costia and trichodina) due to oversalting. These can be treated through other chemical formulas, but you cannot use them in combination with salt.
Using A Salt Dip
A concentrated salt dip is an intervention for a single koi. It increases the water’s salinity to a very high level–essentially as much salt as can be dissolved–for five to 15 minutes. This is only appropriate for very short-term use. Always inspect your koi thoroughly before a salt dip to ensure you are prioritizing the right problem for treatment. We also recommend seeking advice from a professional first.
Salt dips should be administered no more than once every three to four weeks. Never leave your koi unattended during the dip. Additionally, take note of the exact dosing levels for future use.
How to Administer A Salt Dip
First, you will need to find two appropriate bowls or tanks to apply the dip. One will be used for the treatment and the other for respite following the soak. The appropriate size depends on the koi, but water should rise high enough to cover the fish and be wide enough for the koi to fit comfortably.
Prepare the dip by adding salt at a rate of 3 ounces per gallon or until the concentration reaches a salinity of 1.5% to 3%. You can use a kitchen scale to measure the quantity of salt going in and a test kit to check water salinity levels. Stir the solution thoroughly and ensure no salt residue rests on the bottom.
In the recovery tank, add highly oxygenated water or an airstone. It is best to use water from the pond to avoid upsetting the pH balance, which could further stress the fish. Do not use tap water.
Place the fish in the tank for five to 15 minutes and monitor closely for any signs of stress. From there, move it gently to its recovery space and continue to monitor for any issues for 20 to 30 minutes.
Remove your fish from the salt dip immediately if it rolls on its side, gasps, or flaps its gills rapidly. You can try again after diluting the water, but if the behaviors repeat, then a salt dip is not a viable intervention for that koi.
Salt Dip Benefits
Compared with salt baths for an entire pond, which can take days to weeks to finish off harmful parasites and bacteria, a concentrated salt dip can accomplish similar outcomes within just a few minutes. Quick salt dips can also calm and comfort koi during quarantine.
Salt Dip Drawbacks
Dips in very high concentrations of salt are stressful for fish and risk causing severe dehydration. They also do not protect against re-infestation once the fish returns to the pond, as they might not address the root cause of the problem. Finally, though small doses of salt can stimulate mucus, high concentrations can strip the slime coat and make fish even more vulnerable. So consider your treatment options carefully and weigh the pros and cons of salt before administering a salt bath or salt dip for your koi.
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