I think a big problem with guppies is the extent of inbreeding has caused an 'inferior' fish. selective breeding to get the fancy colours and finnage can also lead to health problems and genetic disorders. people have said that when they were kids back in the 60s you could throw guppies in a bowl and they'd be fine, but nowadays it's almost impossible. even feeder guppies have major health problems, like feeder goldfish. they have poor immune systems because they have been raised in less than favourable conditions. personally, i've had enormous problems with fancy guppies, male and female. it seems that pregnancy is too stressful on fancy females and they get very sick when they have babies inside them.