I tell my female pearls apart by looking at their body shape, the shape of their fins and the placement of their markings. You may notice that the slope of the head, especialy - the slight dip on the forehead, and the deepness of the body in females varies from one to the next. Combined with the fact that the length of fins and extended rays (though females don't usualy have many, if any - the extended rays are realy a male characteristic) varies considerably and with the round pearly spots being unique in each fish (both the shape and position), with practice, you can get to know each fish as an individual quite easily - especialy if you have had the privelage of raising them up to maturity from a younger age (you 'get to know' them). With males, the amount of red/orange is usualy what I notice first as a major difference between individuals, as well as the lengths of fins and extensions in the anal fin. With younger ones, tmost of he same as with females applies. Try comparing a few more carefuly at your LFS. If you are realy worried about this, try to pick out a couple of very different females. I guarantee that, though the new additions might be a little difficult to tell apart at first, you WILL be able to distinguish them from your own current female pearl.