IMHO, at least from what my experience has told me (which is all I can
really go on here) that once the fish begins to resemble its respective
adults in color and body shape, they're pretty close, if not ready to
breed. I'm sure there are exceptions to this, but that's what I've
observed over the past. I don't mean full adult color or body shape
(e.g. humped back or blood red fins) but rather a resemblence of their
more mature species-mates. (please allow me to abuse written english)
Just my tow-cents worth.
Mike Adams