Ugh! Clamped Fins and Flashing.

Artist rendition of a Sanke receiving care.

It’s that time of the year again. The water is warm, and it is not uncommon for us in the koi hobby to deal with parasites and infections. Along with flashing and clamped fins, we may also see some lethargy, decreased appetite and unusual skin discoloration.

The internet is overflowing with information on koi diseases but let us break things down into more simple categories. We at Select Ponds like to categorize infections into four main categories that revolve around our major treatment strategies to help our beautiful pets. These categories encompass a vast majority of diseases we will face.

These four categories are visible parasites, microscopic protozoan parasites, microscopic fluke parasites and bacterial infections.

Visible parasites include anchor worm and fish lice. These parasites are uncommon to most hobbyists as reputable dealers can easily spot and treat. In the case you see these visible parasites, the treatment involves manual removal of the parasite or the use of Cyromazine or Dimlin.

The remainder of the parasites are not visible externally, but observation of your koi may reveal rubbing, flashing, or even jumping out of the water as early signs of infection. One of the most essential tools to a koi hobbyist is a microscope. This doesn’t need to be expensive but carry the minimum requirements of 10x eyepiece and 4x, 10x and 40x objective pieces. These can be found for less than 100$ on Amazon.

Microscopic protozoan parasites include Chilidonella, Costia, Trichodina and White spot. These are smaller parasites and with a fresh skin mucous scrape can be identified by quick movements on your slide on higher magnifications. These tend to be treated easily with Formalin/Malachite green treatments such as Proform C.

The other category of microscopic parasites are flukes, both the skin and gill variety. Unfortunately, these require a different treatment. The mainstay for treating these larger, more elongated parasites is Praziquantel. There have been observations the dosing required to eradicate these parasites is increasing due to resistance. At SelectPonds, if we observe resistance in a particular batch of koi, we then turn to Flubendazole. Keep in mind that only the active adult form is affected by the medicine. Gill flukes which reproduce by eggs may require a second treatment around a week later to assure newly hatched flukes will be eradicated as well.

As you may have caught on, our categorization of the parasites revolves around our generalized treatment categories. Of course, each individual parasite carries subtle nuances in their treatment however, we want to help simplify your thought process the next time you see your koi display concerning signs.

Our last category is often a secondary issue to one of the first three categories of parasites. This is our bacterial infection category which we can see externally as ulcers of fin rot. Ulceration could happen without parasite infections if a koi injured itself however it is important to rule out injury because the koi was irritated by a parasite. If the infection is mild, feeding antibiotic food can be helpful. In more dire cases, quarantine with antibiotics or high salt concentration in the quarantine pond or antibiotic injections may be required. Keep in mind that very careful observation of water quality is important should you elect to dose the quarantine pond with antibiotics because the medicines will very likely affect your filtering bacteria as well.

We hope this helps you simplify your potential koi infection thought process. The treatment of diseases in fish can be complex and we certainly cannot address all the nuances of koi diseases in one blog, but we believe this advice can cover a great majority of the common issues we encounter at SelectPonds.

Feel free to contact us if you have concerns about providing the best environment and care for your koi. It would be our privilege to help you care for your koi and help you advance your skills in our amazing hobby.