At 1 " there really isn't any reliable way tell males from females , not for me anyway , males eventually get a hump in the fore head area , some of mine developed at a smaller size then others[3 were as small as say 1 1/4 "and the last guy was almost 2" before he got his ]] . The best thing I could tell you is to buy 6 or so , I bought 6 , thought I had 3 of each sex , one male turned out to be a late bloomer .
I have 2 females out of 6 .
I think they like to be kept in groups , as the Minions read they are a schooling fish .
They are a great little fish .