I have a large, 13 year old koi that has developed a swim bladder problem... or, at least, I think that is what it is. I have had a couple of koi with swim bladder problems over the years. They had difficulty swimming and would spend long periods at the bottom of the pond. Postings on various boards over the years have described koi with those same symptoms. My koi is exhibiting the opposite. She has difficulty swimming, but is spending her time at the surface with her back exposed to the air. When disturbed, it takes some real effort to swim downward. In a few minutes, she is back at the surface. She is eating well, despite having to exert herself to get to the bottom of the pond to reach the sinking food I feed. It seems she has an 'over-inflated' air bladder and has lost the ability to regulate her buoyancy. That's just my guess, of course. It is fairly common with swim bladder problems that the koi develops belly sores from resting on the pond bottom and eventually dies from abdominal infection spreading through the body. It would seem that my koi has low risk of that scenario, but I expect there will be other consequences. Since she does not seem to be in distress, I am just letting her be. I have seen swim bladder problems resolve on their own and will hope that occurs with her, but expect her life span is much shortened.