I've bought tubifex from two places. The first sold worms that stank like anything. I don't want to tell you the trouble they brought us (news included, of course). The second were a totally different story. Even after two weeks in cold water they looked and smelled fine. I was wondering, "Could I take the latter and grow them in my tank alongside adult newts in a plastic separator designed for baby fish, and feed them later to my juvenilles? I would feed only a little clean food like a bit of ground goldfish flakes, and use a bio filter."