With guppies, or I guess, fighters for that matter, most people like the males with their long showy tails. Females are much harder to get rid of in any numbers. You also get a few guppies with deformed spines or tails and personally I dont want to pass these fish on. I agree with Adrienne, if you are going to breed species that produce a large amount of fry, then culling is a fact of life. From my point of view, a sharp blow to the head, or physically cutting off or squashing the head, is a very quick death, while putting a fish in the freezer is much slower.