I have done more reserch and I find that once fish get started picking on other fish they keep it up until that fish is eaten alive or dies and then they eat it then to, kind like chickens, all the other goldies followed suit. The shubys were very agressive but I did not figure they would hurt a koi 3 times there size. I had to drain the pond as I captured the fish the damage became all to clear. even in the holding tank I could see the shubunkins pickin at the koi. one pretty girl had, had the bottom of her tail eaten away until bone was sticking out. I ended up Euth. her with clove oil, I cried for them. :'(. I worked hard to heal the damage to the rest, out of 8 I have 2 left. They will winter in a 1500 gallon pond all alone this year. Next year I will give this pond to my little herd of fantails, and lots of plants.