I apologize that no one has responded to your question sooner. Different experts come online at various times. I just came online and saw your question. My name is ***** ***** I’m a biologist with a special interest in fish. I'm sorry to hear of this incident. I will give you a first aid measure, but first, here are some things to consider.
Have you had any recent thunderstorms? A lightning strike nearby can send a surge through your pump or other electrical equipment and kill fish closest to the equipment. Large koi seem to be more susceptible than small ones.
When you tested the water, what numbers in parts per million (ppm) did you get for ammonia and nitrites? Any ammonia or nitrites will affect fish health. Again, larger fish are first affected. Your pond is probably fine for now, and I doubt this is the problem with Glo, but as the fish grow, you may end up overstocked. I am just giving you this information to prevent furture problems. With excellent filtration, it is recommended to have no more than one inch of koi per 10 gallons of water. One inch per 20 gallons is even better. With overstocking, you'll be constantly dealing with less than optimal water, having to adjust with chemicals, poor oxygenation, and eventually a greater likelihood of diseases and parasites. When a pond has too many fish, there will be one crisis after another. I suggest you read the information on the following website:
Glo may also be suffering from a swim bladder disorder. This is quite common.
The swim bladder is an organ that enables the fish to properly orient itself in the water. When something goes wrong, the fish may float, swim upside down, sideways, or at an angle. . Constipation can be a factor. However, sometimes a swim bladder disorder just crops up for no apparent reason.
It would be best if you can isolate Glo in a hospital tank. A large tote, such as those made by RubberMaid will work well. Use water from the pond and set up a filter or pump with an airstone. Once there, there are a couple of things that may help her. If she will eat, give her a couple of thawed out and peeled frozen peas. The peas can sometimes get things moving again, and ease pressure on the swim bladder. Try holding them right in front of her mouth. Next add one teaspoon of aquarium salt per gallon of water. Don't use table salt - it sometimes has toxic additives. Keep feeding nothing but the peas for a few days. The aquarium salt is first aid for electrical shocks and for swim bladder disorder. Once you take these steps, you will have done all you can, and you will just have to wait and see if Glo will respond.
If you can't provide a hospital tank, it's OK to use salt in the whole pond at the rate I gave you above. If you have more cocnerns, jsut let me know. I hope Glo will be able to reach a full recovery.
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