I hate to post this but, I lost my two koi. Three days ago I replaced my bottom drain to make things better and smaller. I still didn't get the openings small enough. After three days with no problems in the qt we found them inside the pipes, they did not get to the pump ,but they were just too beat up.
Good luck to the rest of you and check those drain openings. This is the first time in four years that I have lost a koi this way. I've never had this problem before.
