An alternative to night crawler are red worm, a smaller species of earth worm that cultivate well in worm bin. You can feed them with vegetative kitchen scrap, a great well to recycle. They multiple very fast and can consume their own weight of food in two days. They don't get dirt in the gut and since they are cultivated in bedding material like peat moss and fed under control condition, I have never heard of parasites problem. Feeding them to small fish do have problem and need to be chop down in smaller pieces and it is a time consuming and messy way.
Here is a link of everything you want to know about how to keep Red Worms.
http://www.wormdigest.org/links/webworm1.html
Here is a link of everything you want to know about how to keep Red Worms.
http://www.wormdigest.org/links/webworm1.html