I used to buy Tubifix worms to feed my tropical fish until one day when the store attendant told me where they come from. They come from the sewers of Mexico. And if you ever smelled them you'd believe it. esp after they've been sitting for a day or so. After that I started raising my own live tubifix worms using a bucket, a strainer and fresh running water. I also raised my own brine shrimp for fish food. At least I had the peace of mind that they were raised under clean conditions.