injured goldfish

Question
For the last 3 years, i have 4 goldfish and 2 koi in a now 55 gallon tank...my koi alerted me this evening to the fact that one of my goldfish was stuck in the aquarium furniture...i had to break the furniture to get the fish out, but i noticed that his fins had been chewed on..not much ,but i think that fish was in a little shock...i took him out and put him in isolation, because i noticed another goldfish nudging and harrassing him..did i do the right thing, or should i trust that the other goldfish understand and will leave him alone????help

Answer
Joseph, you did the right thing by removing the injured fish. While he is in isolation, I would treat the tank with slime coat and add a little aquarium salt to his tank. As for the tank, it is not big enough for the fish you have. The absolute minimum size tank for 1 goldfish is 20 gallons and 10 gallons per added goldfish. With just the 4 in the tank, you are fine. The Koi truly belong in ponds because they can grow to 24". If it is kept in an aquarium of your size, it will stunt the growth of the skeleton, but all internal organ will continue to grow shortening the life span and causing great pain. Please consider either re-homing them or putting them in the right size home.