Updated: Nov 2, 2019
Leeches are cold-water aquatic invertebrates that live in running water, but breathe air and drink mammal blood, one of evolutions little jokes.
Housing: Leeches can live in half-gallon to one-gallon glass jars 2/3rds full of water or small aquariums. Larger is ok, but see the water and cleaning requirements. You can buy an appropriately sized jar at Walmart for about $10. The advantage of jars is that they are easier to clean and have screw on lids. Leeches, lacking bones, can fit through spaces that will amaze you. Just punch a few holes in the lid for air. They will climb partway out of the water to breathe. You may choose to include gravel or tank ornaments if you choose, but the water must be changed frequently.
Lighting: No special lighting required. In the wild leeches bury themselves in mud, and in captivity they are unhappy when well lit for long periods of time, but any ambient light is fine.
Heating: Leeches like cool to cold water and are perfectly happy living in the refrigerator. They also do fine at room temperature in a larger container, which tends to remain cooler than a smaller quart sized jar does. If it gets too hot, the leeches will die.
Feeding: Leeches need to be fed every 3 to 6 months. While we are not suggesting that you need to, it is easiest to feed them human blood. They tend to bite where the skin is thinnest, such as the webbing between fingers, but if you want the leech to bite a particular spot, such as a fresh bruise, you need to prick the skin so a drop of blood emerges and place the leech near it. If the leech doesn’t cooperate it, you can hold it over the spot with a small glass or test tube so it cannot bite anywhere else and it will give up and bite where you wanted. DO NOT try to remove an attached leech, as this can not only damage the animal but also cause them to leave mouth bits in your skin or squeeze blood out of the leech back into your body. The leeches are lab born and sterile and therefore don’t carry disease, but there is no reason to risk infection. Generally they let go and fall off within 30 to 45 minutes. You may attempt to feed pigs blood, but this probably needs to be at room temperature. If you have success, let us know how you did it!
Water: Use chemical free water, such as spring water or distilled water, to keep your leeches. They live in it constantly and chlorine and other water treatment chemicals are designed to kill parasites and will eventually kill them. In addition, do not use declorinator to try to make city water safe for leeches. Using chemicals to neutralize chemicals is not leech friendly.
Cleaning: Leeches shed their skin and poop in their water, so it needs to be changed when it starts to look cloudy or change colors—at least once a week. When you change the water, remove the leech to a smaller, easier to handle jar with water and shack it vigorously. This does not hurt the leech! They live in fast flowing water in the wild and this helps them shed completely. If you see little bands around you leech, it needs to be shaken as these will eventually kill it if not removed. Do not try to remove them by hand except as a last resort, the leech won’t cooperate and you will probably end up feeding it.
Unboxing: If you received your leech in the mail, it is packaged in a small plastic bottle with pinholes in the lid with a sopping wet paper towel. A hungry leech will climb out by itself. If you bought the leech hungry on purpose, you should be ready to feed it when you open the bottle. If not, you may well end up feeding it anyway. If the leech does not climb out and/or was fed before shipping, you can use a knife to split the bottle, just make sure not to cut the leech. If your leech’s home isn’t ready, you can fill the bottle most of the way with water and house it in the refrigerator until it’s new home is set up.