Well, Jungle, I knew there was a lot to learn from your experience.

But, how did the 30" one fit in the bucket????
Joseph: On a serious note, there is an insightful discussion of why there cannot be any "standard" stocking rate for a koi pond in Peter Waddington's Koi2Kichi. The proper rate for a particular koikeeper depends on what they have and what they want to accomplish ...size of pond, filtration, size of koi, desire to show or desire for movement in the garden? Clearly wrong to try to keep a 30" koi in 500 gallons, but for a half dozen 4" tosai being grown for 4 months to select the best to go in a main pond?... 500 gallons might do fine in the hands of an experienced koikeeper, and be a disaster in the hands of a novice.
I kept 16 koi when I had a 2500 gallon pond. I kept between 16 and 18 koi when I had 4500+ gallons. I now have 14 koi in 12,500 gallons...need to find homes for 5 to make room for a couple I'd like to have.