Blackworm – Species Profile

Lumbriculus variegatus (aka Blackworm, California Blackworm) is a species of annelid worm used by aquarium keepers from far and wide as live fish food. The name Blackworm actually covers three species of nearly identical worms that were originally thought to be one species. It can be seen sticking out of the substrate, waving in the current. Two photoreceptors allow it to detect the presence of potential predators.

Care Level: Easy
Preferred Water: pH 6.0 to 8.0
Ideal Temperature: Temperate
Maximum Size : approx. 4″ (10 cm)
Average Lifespan: No Data


Blackworms occur naturally in North America, Europe, and Asia, where they can be found in shallow-water marshes, ponds, and swamps.


Blackworms are detritivores, meaning they feed on dead and decaying organic material. They certainly are not picky, which makes them a popular live food for hobby aquarists to culture for their pets. They can live on vegetable matter, fish food, or even brown paper towels or cardboard.


The primary method of reproduction for Blackworms is by division. If any of the 150 to 250 segments that comprise its body are cut, they can regenerate into a whole new worm. In some places where it is found in the wild, fully adult versions of this worm have not yet been discovered. However, all blackworms are hermaphrodites and can potentially mate with any other member of the species.

If two worms manage to reach adult size and mate, they will produce transparent cocoons. Each cocoon can contain 4 to 11 fertilized eggs. In approximately two weeks, the young will hatch as 1 cm long miniature worms.

In the Aquarium

Blackworms are a popular choice among hobbyists as live fish food. They have no biting or stinging parts, and their soft, slurpable bodies make them well suited to many species and ages of fish. They can be purchased by the pound and stored in the refrigerator prior to use.

Some prefer to maintain a culture of blackworms for their own personal use. They can be kept in a shallow basin of water with little more than cardboard or paper towel to nourish them. A sponge filter and daily water changes are recommended to keep them healthy.

Research Sources:

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Featured image credit: Dvortygirl. Source: Wikimedia


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