There are several keys to ensuring optimal koi fish health. This page is intended to serve as a valuable resource to help koi hobbyists successfully care for these beautiful living jewels that have brought so much joy into our lives.

While koi are relatively hardy fish, they also serve as hosts to various common koi parasites – including costia and flukes, which can often be found during scoping in virtually any established koi pond. While it is impossible to permanently eradicate all koi parasites from any backyard fish pond, there are several steps an experienced koi keeper can take to help keep parasite numbers in check while ensuring optimal koi health. First and foremost, koi immune systems require exceptional water quality provided by sufficient koi pond filtration to function at their best. Care should also be taken not to overcrowd nor overfeed your koi, as the increased fish waste produced can quickly overwhelm your pond filter resulting in unhealthy water quality. The regular use of preventative treatments — including salt, praziquantel, and potassium permanganate can also greatly help to prevent parasite outbreaks in your pond while avoiding unexpected fish losses due to parasites. The use of beneficial bacteria can also help to guard against infections. Large koi fish also require a properly designed koi pond in order to thrive, and contrary to what you may have read elsewhere – a koi pond and a water garden are NOT the same thing!  Practicing sound koi quarantine procedures for all new koi additions before adding them to your main pond is also strongly recommended regardless of source.

Proper Koi Pond Design:

A shallow planted water garden full of rocks and gravel is NOT a proper koi pond.  Trying to safely keep large koi in a typical Aquascape water feature is a recipe for disaster. And regardless of what your “certified” landscaper may claim during a sales pitch, large koi will NEVER find “balance” in a hastily built poorly designed water feature.

Sufficient Koi Pond Filtration:

A skimmer filter, waterfall filter or small canister filter are NOT sufficient for large koi fish and the waste they produce.

Weekly Pond Maintenance:

Be diligent about cycling your pond filters at least once per week,  while also doing partial water changes. This is critical to maintaining healthy, clear water for your beloved koi.

Avoid Overstocking and Overfeeding:

The more you feed your koi, the more waste they produce and this can wreak havoc on pond water quality. Koi collecting can become quite an addicting hobby, but you must show some restraint if you with maintain optimal koi health.

Preventative Treatments for Parasites:

Understand that common koi parasites — including Costia and Flukes exist in virtually any established koi pond and parasitic outbreaks can occur very quickly.  The use of preventative treatments can greatly help to keep parasite numbers in check.  We highly recommend keeping salt, praziquantel and potassium permanganate on hand at all times.

Quarantine Procedures for New Koi Additions:

Follow sound quarantine procedures for all new koi additions before adding them to your main pond.  Used Rubbermaid stock tanks or small Intex swimming pools work great for this!

Recommended Must-Have Treatments for Every Koi Keeper:

We strongly believe there are three effective preventive treatments every experienced koi keeper should keep on hand at all times.  These treatments include (1) salt, (2) praziquantel, and (3) potassium permanganate (PP).  

Salt: Effective and relatively safe treatment for most common koi parasites

Maintaining a salinity level of .04% (4 pounds salt per 100 gallons water) for 5 days will kill most common koi parasites, including most cases of costia and flukes while also increasing koi slime coat (increased immunity).  Unfortunately, sometimes parasites can become resistant to salt.  In these cases, we recommend using praziquantel for salt-resistant flukes and we recommend using potassium permanganate for salt-resistant costia.  

Praziquantel (Prazi): Very effective and safe treatment for salt-resistant flukes

Apply one gram praziquantel per every 100 gallons of pond water.  Repeat praziquantel treatment once every 7 days for a total of 3 treatments spread over 21 days to eradicate adult salt-resistant flukes.  It is very important to realize; however, that praziquantel does NOT kill fluke eggs so it is entirely possible flukes will ultimately return so you should plan on repeating this same treatment on a seasonal basis or whenever issues occur.  

Potassium permanganate (PP): Very effective treatment for salt-resistant costia

Sufficient aeration is required when using PP so be sure to have your aerator pump running.  Apply two level teaspoons PP per every 1000 gallons pond water.  Wait 4 hours then do a 20% partial water change.  Use hydrogen peroxide (8 oz. per 500 gallons pond water) to deactivate PP instantly if you encounter any issues during treatment.  Repeat this same PP treatment two days later (day 3), then apply a third treatment on day 5 to eradicate salt-resistant costia.  If you do not wish to treat your entire pond, you can also do a PP dip for the specific koi you are worried about.  For PP dip, add 1 gram PP to 5 gallons of water in a separate tank with an aerator pump.  Place desired koi into this tank and observe them closely for 7 minutes.  Again, use hydrogen peroxide (4 oz.) to instantly deactive PP if you encounter any issues during treatment.  After PP treatment, briefly place koi into separate tank to rinse off excess PP then release back to pond.     

We hope you have found this page to be useful. Southern California Koi Rescue is a registered non-profit animal rescue specializing in koi fish and other pond pets. Since 2008 our dedicated volunteers have completed hundreds of large koi rescues throughout CA, NV, and AZ while successfully finding new forever homes for thousands of beautiful living jewels. For those interested, charitable donations can be made via our Donations page.