Hi, all! I have just a small pond, a 300 gallon stock tank, but I have been keeping goldfish and koi for years. I take my fish in for the winter. Last year I had to rehome my lovely 15 in. Koi, since she had grown too large to be happy in this habitat. She ended up in a fantastic big pond where she could really flourish. After she was gone, I said no more koi, just stick to goldfish. But I added a couple more small koi, just could not resist when I saw some that caught my eye. Lol, they are growing fast!