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Leeches in Blackworm (Lumbriculus variegatus) Cultures – observations on their value as aquarium scavengers

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:

Thanks Frank!


About Frank Indiviglio

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Being born with a deep interest in animals might seem unfortunate for a native Bronxite , but my family encouraged my interest and the menagerie that sprung from it. Jobs with pet stores and importers had me caring for a fantastic assortment of reptiles and amphibians. After a detour as a lawyer, I was hired as a Bronx Zoo animal keeper and was soon caring for gharials, goliath frogs, king cobras and everything in-between. Research has taken me in pursuit of anacondas, Orinoco crocodiles and other animals in locales ranging from Venezuela’s llanos to Tortuguero’s beaches. Now, after 20+ years with the Bronx Zoo, I am a consultant for several zoos and museums. I have spent time in Japan, and often exchange ideas with zoologists there. I have written books on salamanders, geckos and other “herps”, discussed reptile-keeping on television and presented papers at conferences. A Master’s Degree in biology has led to teaching opportunities. My work puts me in contact with thousands of hobbyists keeping an array of pets. Without fail, I have learned much from them and hope, dear readers, that you will be generous in sharing your thoughts on this blog and web site. For a complete biography of my experience click here.