I have a 9 yr old koi on side. Was good thru winter then we had a thaw and refreeze and she is now on her side not looking good. If we try to catch her she does take off. Water tests are good. We opened our pond and did a water change, all the while she was swimming upright. She will go upright and swim around the pond but then comes to top and on side. She is a good 27 inches long and the queen of the pond. It does look like some streaking in tail. We are still cold here so don't want to try to feed peas as other sites suggest. I really can't stand the thought of loosing her. Others in pond seem fine but I did loose 3 smaller ones this winter. We have no one in area that I know of who specialize in koi so I am on my own.