i have a double sword guppy exactly like the one in your avatar.....
been alive for a long time !
i have one little guppy... i think shes a feeder because shes pretty small.... she never grows, but has babies every 4 weeks... ive had her for about 2 months and shes had 3 batches of fry already... and shes really fat again.... ive never had a female that bred this prolifically... and her fry are troopers too.... from her 3 batches in a 10 gallon with 15 adult guppies, about 30 of them survived... which is pretty good i think.... shes really small thought i dont know why she wont get bigger but doesnt bother me aslong as she keeps breeding the way she does..... her 2 oldest fry are both females also... and after about 2 months of life, theyre almost her size.... i also have a bunch of black finned babies... but i dont think they came from my males ... i dont have any black finned males in my tank.. so i guess it was from a male in the tank she was in at the pet store