I started a worm farm of my own so I wouldn't have to worry about any potential contaminants from outside worms. Worms used for composting are eisenia fetida, aka redworms, or red wigglers. Worm farm suppliers sell them by the pound, or you can usually buy them at pet stores. There are specialty worm bins you can buy, or you can DIY one pretty simply. Just take a plastic bin, preferably a wide and shallow one, drill drainage holes all over the bottom, place a piece of landscape fabric over the bottom to allow excess moisture to escape but still keep the worms in. Put your bedding in with a small amount of soil, usually coco fiber, but you can also use shredded newspaper. Poke holes in the lid for ventilation, and put it in a cool, dark place. Then just start plopping your kitchen scraps on the top. Vegetable matter only, and nothing really strong or acidic, like citrus fruit, onions, hot peppers, etc. As long as you stick to the right kinds of food, it won't stink at all, it will just have a mild earthy smell that you can't even detect until you take off the lid. Change out part of the bedding periodically once it gets full of worm poop, and use the old stuff to fertilize your plants. I started with just a couple little tubs of worms from the pet store, and now I have a whole bin full of squirmy friends that reduce the amount of trash I throw away, and provide occasional treats for my fish.