Summarize the following:
Visit a local fish or animal store and invest in a fish tank. Leeches are adept at living in close quarters—at the most, about 50 can live comfortably in 1 gallon (3.8 L) of water. However, this ultimately depends on the type of leech and their environment of origin.  In general, 50 leeches at most can live in a 10 gallon (38 L) aquarium. Pond leeches do best with 1 to 2 leeches per gallon. If you catch leeches on your own, use a small dip net to collect them from a pond or remove them gently using forceps. You can also visit a local bait store of science supply shop to buy them. If you buy leeches from a store, ask the staff about what kind of food and space they require. Leaving some space free at the top of the aquarium creates a barrier to stop leeches from escaping. Always use spring water, dechlorinated tap water, or water from the collection site. Never use purified water or chlorinated water—the former is harmful to the leeches' metabolic balance, while the latter contains harmful substances like copper and chlorine.  Be sure that the water is cool and clean. To get rid of chlorinate in tap water, fill a container with the water and let it set for 1 to 2 days. Once the smell of chlorine fades, you're good to go! You can also purchase a water dechlorinator from a home hardware store. A temperature range of 76 to 80 °F (24 to 27 °C) is recommend for most aquariums, but you can widen this range a bit for leeches. In fact, they can tolerate quite a range of temperatures—anywhere from 40 to 80 °F (4 to 27 °C). A submersible or hang-on heater are the best options for temperature maintenance.  For small tanks, make sure the heater is 5 watts per gallon. Larger tanks require about 3 watts per gallon. Keep an eye on your tank's temperature regularly and adjust the heater as necessary to keep it within the proper range. You can pour more if you'd like, but around 2 inches (5.1 cm) is a standard amount. This gives your leeches places to hide. You can also add shells and plants for some variety!  If you get your leeches from the pond, take some plants from the area around it and add them to your tank. Purchase shells and plants for your tank from pet stores. Gently pour your leeches into the tank. If you have a small amount, you can also place them in one-by-one with forceps. Always secure the top of your tank with a tight-fitting lid, such as a screen lid. Leeches have the ability to lengthen their bodies and squeeze through small openings—never skip the lid! Purchase a screen lid from a local pet store or online supplier.

Summary:
Purchase a glass tank that is at least 1⁄2 gallon (1.9 L) large. Catch your leeches from a pond or buy them from a bait store. Fill the fish tank 75 percent of the way with water from a pond or stream. Keep your tank's temperature between 60 to 70 °F (16 to 21 °C). Pour 2 inches (5.1 cm) of gravel into the bottom of the tank to create hiding places. Put your leeches in the tank and cover it with a tight-fitting lid to prevent them from escaping.