Guppy Fry Maturing

[guppygirl01]

I've always sold my fry to people who want them as newborns. When do they actually mature and when do they get their full color? What are the odds of me getting a guppy with a spotted tail from two guppies without it. I want to wait until they are fully mature this time. Well at least until they get their full color. So, how long should it take?