from what I have noticed with my geos..which are mostly abalios, with one altifron, there is no specific age or size for when they start breeding. There are so many factors that go into breeding. it has to be the right setting, right tank mates, how comfortable they are, how big the tank is, how many tank mates there are, etc...for example, I had a 4.5in female abalios breed a few weeks ago and I'm taking care of the babies now and I picked up two 9in and one 10in abalios about 3 months ago and as soon as they got into my 500g they started breeding for the first time. So it all depends. Maybe someone else has a more precise answer, but with my experience, there are so many different factors that come into play.