Leeches are annelids, which feed on organic mater. Although they are best known for drinking blood, most leeches feed on dead tissue and small invertebrates that they can consume whole. Those that feed on blood only attach to a host organism long enough to feed and drop off on their own when full. Some leeches are used to treat medical conditions such as clots. This process is called hirudotherapy. These creatures, called hemophagic leeches, are kept and bred for medicinal uses.
Get healthy medical-grade leeches, and keep them for a period of at least two years before you breed them. They reach sexual maturity sometime between two and three years of age.
Feed the leeches every 20 days. Give the leeches a blood sausage, housed in an intestine. Bovine byproducts are most commonly used to meet these dietary needs.
Keep the leeches individually in about 100 cc of water in the months before you begin breeding.
Put two leeches together in a shallow pool or 1-quart aquarium with a layer of peat moss in the bottom. The peat moss should slope across the bottom of the tank so that there is a shelf of peat moss above the water level on one side. The water should be fully dechlorinated and at a temperature between 68 and 77 degrees. You do not have to worry about the gender of the leeches because they are hermaphroditic, having both male and female reproductive organs.
Allow the leeches to remain together and copulate for a full 30 days. Watch for the leech to lay the egg cocoon. It will lay eggs in the peat moss just above the waterline on the side where the peat moss forms a shelf. This can take anywhere from one to nine months, depending on how long the mother leech stores the sperm before breeding. Leeches will lay between one and five cocoons that house between three and 30 eggs each, but which typically contain no more than 15 eggs each.
Wait three to five weeks for the eggs to hatch. The little leeches will be between 0.12 and 0.18 grams at the time of hatching and will grow over the course of two years before they are mature enough to be used for medicinal purposes or breeding.