Please welcome back Frank Indiviglio with another article.
Those of you who use blackworms as fish or amphibian food have likely been surprised (or horrified!) to find small leeches in among the worms. My own curiosity and questions from others led me to take a closer look. Upon doing so, I was amazed to see the leeches sucking down the blackworms like spaghetti!
Leeches are, of course, best know for their blood-sucking ways – but it turns out that a great many of the over 650 species are actually predatory (although the largest, the giant Amazon leech, Haementaria ghilianii, does suck blood – and, at 12 inches in length, quite a lot of it!). Blood sucking forms, it seems, evolved from predatory leeches.
I established a colony of the leeches in an aquarium and found them to be exceptional scavengers (as are blackworms themselves). They emerged from the gravel bed at night (they are sensitive to light – I was able to best see them by using a night viewing bulb) and made short work of dead fishes and leftover food, and were very effective at reaching areas below rocks and the filter. They showed no interest at all in the loaches, African clawed frogs, snails or shrimp that shared their aquarium (at least while the foregoing were alive!). The leeches deposited their eggs in a case attached to the undersides of rocks. The egg case’s covering is tough and leathery, and obviously offers good protection against predators.
I believe it would be worthwhile to investigate the use of this leech as an aquarium scavenger. I am still uncertain as to the species, and had one unexplained die-off, and so would greatly appreciate hearing from anyone who might have further information. Thanks. Until next time, Frank.
General information on leeches is available at: