Leeches
Though they are not exactly what comes to mind when you imagine the ideal aquatic pet, leeches are nonetheless fascinating creatures, especially for those people who lean toward the unusual in their interests. Although their habit of feeding upon the blood of living creatures is well known, most species are actually predatory by nature and feed upon other invertebrates. All leeches are equipped with two suckers, one at the head and one at the rear of the body, by which they move about and attach themselves to their victims. Closely related to earthworms, leeches are best known as aquatic animals, but, in fact, several species are terrestrial. These types inhabit tropical rainforests and find hosts by anchoring themselves on plants along trails used by other creatures.
Leeches were used in earlier times to remove the “bad blood” that was thought to make people ill. You may be surprised to learn that thousands are still used in modern medical practice to prevent blood from coagulating in certain types of microsurgery.
Leeches are quite undemanding as pets, having relatively low oxygen and food requirements. The needs of most can be met with a small piece of meat or earthworm provided once every two weeks. Leeches have been said to have survived in sealed glass jars of water with no food or supplementary oxygen for periods of up to one year (don't try this with your own leeches!). Despite their rather “simple” appearance, leeches are quite alert to the presence of food. The tiniest bit of meat or blood placed into the water will induce an immediate and frantic search for the source. They unerringly arrive at the food item in a very short time. An interesting experiment is to rub your finger along the bottom of their aquarium. Heads raised, the leeches will crawl around until they reach the spot where your finger was, and where the scent is the strongest, whereupon they will search for its source. Hungry leeches will also respond to a shadow passing overhead, rousing themselves to search for the “fish” that produced the shadow. One species of leech often arrives in aquariums mixed in with black worms that are fed to fish. This type favors black worms as food, sucking them down with gusto. Once established in an aquarium, they are quite difficult to remove. Their hard egg cases are nearly impregnable to attack by fish or other animals. They generally burrow below the gravel and, in fact, do a great service by being excellent scavengers. They especially favor fish, and any fish that dies in the tank will be reduced to bones by morning.
