Bloodworm Larvae in Koi Ponds

As their name says, bloodworms are a blood-colored wormlike creature measuring about 1 millimeter long. These wiggly aquatic worms are a common sight in standing bodies of water, and though they might seem intimidating, they are usually not a cause of alarm. Actually, bloodworm larvae can be helpful to your koi pond.

Kinds of Bloodworms

“Bloodworms” can refer to the seams of a nonbiting midge (Chironomidae) along with the parasite also called blood flukes (Schistosoma). Even though chironomidae aren’t harmful to individuals, unless the man or woman is allergic to these, schistosoma — which is not found in the United States — has infected over 200 million individuals worldwide. Schistosoma, detectable only under a microscope, which is usually located throughout Africa, South America and Asia. This parasite lives in certain species of freshwater snails and contaminates the water.

Nonbiting Midges

The bloodworms in your koi pond are the pillars of nonbiting midges known as chironomids. These insects resemble tiny mosquitoes but don’t bite people or feed on blood. Nonbiting midges lay their eggs on the surface of ditches, streams and ponds. These eggs sink to the bottom of the pond and hatch a couple of days later. The larvae, known as bloodworms, consume organic matter in the pond, which helps maintain the water clean and clear. Bloodworms generally transform in the pupa stage about two to seven weeks following hatching. They remain in this stage for about three days before swimming to the water surface and also appearing as an adult chironomid.

Bloodworm Larvae and Koi

Bloodworms in your koi pond aren’t something that needs concern. The larvae don’t harm any plants growing in the pond and also are beneficial in many ways. As well as helping to keep the water clean, bloodworm larvae are a food source of fish like koi. Bloodworm larvae are high in proteinthat is essential for healthy koi. Frozen bloodworms are offered for purchase at pet stores, and also some pond owners increase bloodworm larvae for use as food for their fish.


If bloodworms aren’t welcomed guests, several control options are available that won’t hurt the koi. The bacterium Bacillus thuringiensis var. Israelensis targets only the pillars of specific pests, like nonbiting midges, and will not hurt the koi fish in the pond. Another option is to attract predatory insects to feed the nonbiting midges. Dragonflies and damselflies prey on the adult midges while their larvae feed on the bloodworm larvae. Submerged, marginal and floating aquatic plants added in and about the koi pond lure dragonflies and damselflies into the area.

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