I am hoping someone can help. When feeding the fish today I noticed that one of the kois was eating strangely, then when it turned I saw that on one side of its face was deformed (I hadn't noticed this before today). I researched the symptoms it was showing and it looks a lot like mouth rot. I am currently doing a water change in the pond, so can't measure the water levels, but I will describe the pond. It is 16x12x4 feet (4784 gallons), using a PondXpert SpinClean 20000 filter, as well as having a waterfall running from a small pond filled with watercress. The main pond itself has lots of oxygenating plants, there are around 8 koi, 10 gold fish, 3 or 4 rudd, a shoal of minnows, and a few stickleback. I haven't been able to catch the ill koi yet, but want to know if mouth rot is contagious? What is the best method to rid the pond of parasites? Any advice/help would be greatly appreciated, thank you in advance.
Just updating to say that sadly the koi had to be euthanised this morning as the mouth rot had gotten into its bone. However, all of the other fish are perfectly healthy. I can only assume that the infection was caused by the algae bloom from all this sun we have had, as well as slight overfeeding.
Sorry that no-one has responded before now. I'm not familiar with ponds or koi health, having had no direct experience with them. I might have suggested isolating the fish (if you had a container big enough plus a filter) and treating with a wide-spectrum treatment like eSHa 2000 or Waterlife Myxazin, although a quick google search suggested a number of alternative options. However, it sounds as though unfortunately the fish wouldn't have made it, even if you had tried what I might have suggested or anything else, given that the bone was affected. Sorry for your loss but it sounds as though euthanasia was the kindest mode of action under the circumstances.