I culture red wiggler worms (AKA composting worms) - super easy, safe, nutritious and readily accepted by every fish I've tried to feed them to.
My culture is in a bin in my garage. I drop our family's veggie and fruit scraps and shredded junk mail.
Haven't bought live or frozen food in years.
It takes a couple of months for baby convicts to grow to decent size. In warm weather, red wigglers will double every week or so...
Matt