The Princess and the Pond

In every veterinarian’s career, there will come cases that try us mentally, physically and emotionally. For us here at Aquatic Veterinary Services, we have been tested by a case that we battled for almost 6 months. What started as a simple lesion steamrolled into a serious bacteria problem for multiple large koi.

Princess, a 28″ kohaku koi, had been moved with 5 of her pondmates from Redding last fall down to Carmel. Early in their acclimation, one of the koi got sucked up into the filtration and was killed. The fish were moved temporarily to another pond for a few weeks before the problem could be fixed and the fish returned. One of Princess’s cohorts, Whitey, started to have a small red spot on her nose. In addition, Princess started to have a red mark next to her left pectoral fin. Physical exams showed a penetrating pectoral ulcer on Princess’s left pectoral muscle. Princess received an antibiotic injection and would receive a re-check in a few weeks.

Princess (left) & Whitey (right)

A few weeks later, Princess’s wound had not improved and now Whitey also had signs of a nasty ulcer on her right pectoral muscle. A culture was taken from Whitey’s wound and the owner elected to treat with an aggressive 8-hour dose of potassium permanganate. Due to the high algae load in the pond, the first PP treatment required two smaller, follow up doses in order to keep the pond purple for the full treatment. Even with the treatment, the fishes’ wounds did not start to improve. In fact, two other fish in the pond were starting to show signs of a persistent infection. One had fractured a fin ray that caused a massive hole and the other’s eyes started bulging out.

Well, when the culture results arrived, we found out why the fish were not responding. Two drugs, out of the dozen processed, would be able to kill the Aeromonas spp. present. Two, out of a panel of twelve. One of the drugs would cause kidney failure if used at too high a dose. The other was only available as a powder for oral dosing. We were able to make up a medicated feed with the powder, but unfortunately, the fish decided that it was not to their liking. Some drugs are very noxious and fish will not eat them, even when we try to hide them with flavorings. So, that left us with one drug, but only one dose taking careful weight measurements so as not to incite kidney failure. All 5 fish in the pond received injectable medications.

Did it work? Not really. Many of these drugs require repeat doses in order to be truly effective. At this point, we were left with very, very few options. This is the part where I stay awake at night thinking, ‘what else can I do?’ Thankfully, when we were trying to come up with some sort of alternative plan, the powder antibiotic was finally available as an injectable! We bought as many vials as we could and we managed three rounds of injectable meds.

Keep in mind that all of these injections were done in the pond without sedation. We also had to give all of these fish physical exams every visit, without sedation. You try holding a 25 lbs slippery rocket made of pure muscle and see how long you get to stab it with a needle. I am so proud of myself that I was able to give these fish the care that they needed with the limited options we had available.

Long story short: every fish is now on the mend. Are they healed entirely? No, not yet, but all of the wounds are showing great signs of proper healing. Thanks to their very patient owner and our unwillingness to give up. These cases don’t come around very often, but when they do, we are so glad to report a happy ending for this pond.


  1. Determination and genuine caring pave th road to your success…so proud of you and your team!! Joan

  2. Thanks for telling us all the tale of the lovely Princess and her mates. Veterinary medicine can be truly frustrating. But you hung in there and got those lovely creatures well. Congratulations on a job well done and a story well told. Will be anxious to see how the pond mates fare in the future. Please do keep us koi kichi folks out here informed.

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