Fancy guppies, seem to do better for me, in warmer, 78 to 82 degrees F water than the more common guppies who seem to fair well in wider range of temps .
Both need fairly hard water.
Young fry and adult's I have/am cared for, accept regular feeding's of algae based flake foods such as Omega one veggie flakes,and occasional DRIED bloodworms ,daphnia.
The Fry also appreciate floating live plant's such as Water sprite,Anacharis,or Pennywort which over time will harbor all type of infusoria and perhaps some algae, as well as give the fry place to hide and comfort.
Would were it me,,use nothing smaller than ten gal tank'sand sponge filter's.
my expierience with offering feeder fish to larger predatory fishes has been that if fed more than once a week,,the larger fish can sometimes refuse more healthy prepared foods once they get the taste of feeder's imprinted on their small brains.
Hope some of this helps.