i dont currently have any endlers, but did keep them for about 12 years. when i first got them, for the first year or two i could not get them to breed, no matter what. after i gave up on them, and lost them all i went back to guppies, but there must have been a surviving baby or two, because after a short while i had endlers everywhere, to the point i couldnt give them away fast enough.
endler females seem to run bigger than the males, but even if your females are guppy, guppies and endlers cross breed quite easily.