Can you feed guppies naturally?

Hey there, I'm wondering if there's a way to grow and breed guppies without having to buy tons of expensive feed for them.
I'm playing with the idea of feeding them to my poultry (ducks, chickens, and geese) to help offset their feed cost, and add more diversity to their diet. I've read that they breed super fast, and without much encouragement. Is that true?
I have a really big indoor tank, and all the filtering stuff, but I can't find anything on feeding them DIY. Everything I've read online says you have to buy pre-prepared food.
Are guppies the right choice? I like them since they make for a nice looking fish as well as fast growing food, but I'm open to other options. I've thought about goldfish, since we raise them in our heated cattle tanks year-round, but they have never reproduced. Plus I think they'd be too big for the poultry to eat effectively. We've also thought of trying snails, but I like the idea of doing fish as well since it could be a fun way to feed the waterfowl more naturally.
I live in Wyoming, and it gets too cold for them to live outside for most of the year, which means we can't use mosquito larvae as a consistent food source.

Guppies are a super easy breeding fish, the biggest challenge is making enough hiding spaces the adults don't eat all the fry. And if you kill off all the males by mistake, don't worry - the females store sperm and will continue making babies anyway.

Food, the hardest part would be the size. You want that food in very tiny pieces, I'd use a blender. They're omnivores, they'll eat just about anything. They need some protein, and, if you don't have enough healthy algae growing in your tank, a little green stuff.

I stumbled upon a YouTube channel Dexter's World. He lives in the tropics somewhere and supplies his own pet store with his breeding programs. Currently he is working towards a freerange system for his Fish and animals. Perhaps you could glean useful information from there.

YouTube channel

Maybe brine shrimp or mosquito larvae...you could breed and freeze those as well.

My husband set up outdoor tubs this year with white cloud minnows and Japanese rice fish (separate tubs).  One was about the size of a bushel basket, the other was a cut off rain barrel on its side, about the size of an oil-drum bbq grill. The tubs had plants also.

Both the minnows and the rice fish reproduced in great numbers. He did occasionally throw them some food, but mostly they ate larvae, algae etc.  These are fish that in milder climates where tub won’t freeze totally solid can stay out all year.  We live in Chicago, so he put them in indoor tank in basement for winter.

Either of those might serve your purpose.