I have a tank full of mickeys and fancy-tailed guppies. The female guppies don't bother with the mickeys, but the male guppies do try to "mate" with them because to them it looks like a big fat female guppie in "heat". Guppies watch the females for swollen and darkened bellies to mate (which with them is ALWAYS), so you can see where they get confused. I've never had to separate them though, so I guess it depends on your tank situation.