It has to be a carp in "heat". It is killed (humanely, I assume) and its pituitary gland is removed and the hormones are extracted with a solvent. That extract is what is used on the parents of the future hybrid. It can be added to water but it is much more efficient if it is injected into the parent fish.
Yeah, cichlids breed mostly "naturally", more or less, so the cichlid example, as you stated, is outside of the scope of this discussion, I think.
Yeah, cichlids breed mostly "naturally", more or less, so the cichlid example, as you stated, is outside of the scope of this discussion, I think.