We had about a dozen koi fry make it to a decent size last summer. Some of them are black and blend right in with the rocks, so it was difficult to get an exact count--the best we could do was try to count when they were feeding in one spot, but they move fast. Our pond is about 750 gallons, so I don't want the pond overcrowded. We gave about half of them to a friend of mine who has a pond too, and so far two have died this winter.