This is going to sound crazy so hold on: cut a potato in half scratch out the center to form a cup bury it in the ground maybe 8 inches or so in soil not sandy rocky stuff wait three or four days. Wrote you dig up the potato make some mushy oatmeal I mean just as pudding like as you can get it let it cool. There will be worms in the rotting potato that’s the start of your culture. Put some of these in a ventilated container with the mush. Warning this will not smell good keep in cool dark place harvest worms at your own peril. Lol I did this as a teen my mother was not happy but my neons loved it.