I'm not certain of the original intent of this thread but here's my
solution for a natural control of one's fish load, a solution that I
stumbled onto accidentally. I built my pond in about 1998. I added
comets, mosquito fish and koi. After the first year my fish population
nearly doubled. I was concerned that I would have to euthanize
excessive fish that I was unable to give away and I didn't like the
thought of killing them. As the mosquito fish multiplied, and they do
so like rabbits, I noticed they must be keeping my fish population in
check by eating the spawn each Spring. Just enough eggs escape to keep
my pond balanced to replace those few fish that have died. Thus, since
I built the pond I have not had to euthanize fish or purchase any new
fish. The mosquito fish population also remains balanced; how I don't
know, but they do. And as far as mosquito fish being "fin nippers",
not so with my skeeter fish.