Shane, Koi won't breed until they are 3 to 4 years old. They are usually 18 to 24" when they start to breed. You won't start to get 200,000 babies until the fish is around 30 to 36" long.
Mike

lol thanx mike, in a 11'X8'X4' pond I dont think ill get any koi that size eh!
Shane

Shane, Why not. I have seen people raise three koi that size or bigger in a 100 gallons of water.
Mike

I must have been misinformed then, I was under the impression that they only grow to the size their environment allows, and I just figured from that that I would end up with some in the 12-18" range. Those are very big fish for a 100gal eh.
SHane

Shane, Fish put a chemical in the water and as the concretration of that chemical gets high enough they stop growing and having babies. By doing enough water changes the chemical doesn't get high enough and they keep growing.
Mike

Very interesting, Mike!