At quite an early age the anal fin on a male guppy or most live bearers gets to look a bit like our own equipment in minature and on the female there is a dark patch behind the anal fin!. Also as I understand it the have about 3 lots of young from one mating,aned up to 90 young at each birth.The adults will scoff the young as fast as they pop out ,angels love em!feed the young on liquid livebearer or as was said crushed flake!!.