Guppies need plant material in their diet... An easy food for them is as follows:
Buy baby spinach, some raw zuchinni, chard, and other nutritious green vegetables.
In a pot of water (1 - 1 and a half cups of water), add 1 multivitamin tablet, 1 packet of Plain gelatin(optional) and garlic (fresh, minced, powdered, doesn't matter.)
Bring to simmer while you slice the zuchini thin, and break large leaves into small pieces a couple inches across.
Turn up the water slightly until it just boils.
Add all the vegetables to the water. (You can also add raw minced shrimp, crab, earthworms, or freshwater fish that isn't fatty too, but for livebearers, 1-2 minced shrimp is plenty for a heaping cup of vegetables)
Boil for 2-3 minutes, stirring gently.
Remove from the water, and freeze in small portions.
Alternatively, add all veggies and meats to a food processor and chop super fine. Add a couple spoonfuls of the water and a packet of gelatin, and blend. Yo I may need more liquid. You don't want a puree, but you want the gelatin dissolved. Pour or spoon into an ice cube tray and refridgerate for 2 hours, remove from tray, then freeze.
I feed my tanks a small bit of this mixture once a week or so.