They are easy to keep and safe for fish. Google microworms you will see lots of videos.Are they hard to keep/breed? Do they carry any unwanted organisms that would be harmful to fish, shrimp or snails? I haven't used them before, just bloodworms.
They will come maybe with a little substrate but no. you will need to make up 2 or 3 tubs at your house. Most common methods areWell, i'm game try it. Pm me with details. Do they come in a substrate or whatever already?