Chironomid larva, commonly known as ‘Bloodworm’ is a major natural food for many species of freshwater fish, crabs, crayfish, axolotl, frogs, and even shrimp. The valuable nutrient-feeding composition of bloodworms made many aquarists think to themselves “How difficult and expensive would it be to produce my own bloodworms?”
Although bloodworms are relatively hardy, rearing them (full cycle) in home conditions can be problematic because of their dual mode of life in water and in the terrestrial environment.
This article provides valuable insight into the life cycle and culture of Bloodworms for the purpose of feeding aquarium fauna.
|Interesting fact: Chironomus larva is a well-established model organism in various fields such as ecotoxicology, biology, and ecology, due to its high fecundity, low maintenance cost, rapid development, and high tolerance to various environmental conditions.|
What are Bloodworms?
Bloodworms are the aquatic larvae of non-biting midges (family Chironomidae). This family is estimated to comprise more than 10000 species in the world and is found in various environments from the high Arctic to the Antarctic, in a large variety of habitats. This is the most abundant group of aquatic insects found in freshwater ecosystems.
Although the more common and available bloodworm species for culturing include:
- Chironomus reparius
- Chironomus decorus
- Chironomus plumosus
- Chironomus thummi
Obviously, it is close to impossible for an ordinary hobbyist to find out what exact species they may have in their place. Luckily we do not need that. All we need to know is that they are bloodworms (not pest worms) and it can be done pretty easily.
How to Identify Bloodworms
Size. Bloodworms (Chironomid larvae) have elongated cylindrical bodies, generally, varying in size between 0.2 to 1 inch (5 – 25 mm) in length.
Movement: Bloodworms move in a characteristic twitch that resembles “S” letter.
Diet: They mostly feed on green algae or detritus.
Color: These larvae are named Bloodworms because they are red in color due to the presence of Hemoglobin (Hb) in their body fluid. This pigment gives them a red color.
Note: However, the main function of hemoglobin is to take up oxygen in low-oxygen waters. It allows bloodworms to survive in low-oxygen environments at the bottoms of ponds, lakes, swamps, etc. In the complete absence of oxygen, chironomid larvae fall into a state of suspended animation.
Body structure: Their body is divided into thirteen segments and can be divided into two main parts: thoracic region (first three segments) and abdominal region (the next 10 segments). Segmentation can help the bloodworm move.
- The body is smooth and has a thin and transparent cuticle.
- The thoracic segment has one pair of false legs bearing chitinous hooks. They use them to move along the substrate and also build tubes (casts).
- The last segment of the abdominal region also has small false legs which are used to move.
Life Cycle of Chironomidae
The life cycle of Chironomidae comprises of four stages and is usually completed within 3-6 weeks.
|Stage 2||Aquatic||3-4 larval instars* (Bloodworms)|
|Stage 3||Aquatic||Pupal stage (transitional stage)|
|Stage 4||Aerial||Adult stage (Midge)|
The 3rd and 4th stages are very short time periods. The adult stage only requires a mating process, egg formation, and oviposition. The largest part of their life occurs during the larval period (as Bloodworms).
Note: Instar is a developmental period of larvae in insects.
Stage 1: Eggs
Oviposition usually took place early in the morning. As flies, pregnant females deposited their eggs just below the water surface.
Depending on the species, each female can lay from 100 to 2000 eggs.
For example, Chironomus plumosus can lay on average 1600 eggs. Whereas Chironomus Xanthus can produce around 500 to 600 eggs and Chironomus riparius has an average number of 400 eggs per female.
Eggs are involved by a gelatin-like cocoon and are arranged in a spiral-shaped mass. When in contact with the water, the eggs start to absorb water, swell, and sink to the bottom.
At an incubation temperature of 75 °F (24 °C), after approximately 48 to 72 hours, the larvae begin hatching. Under lower temperatures, it can take up to a few weeks to hatch.
Stage 2: Larval instars (bloodworms)
The first instar bloodworms are colorless, free-swimming, and positively phototrophic. Generally, they just remain among the substrate particles, feeding on bacteria (filter feeding). Basically, this is a planktonic stage. This stage usually lasts 2-4 days.
The second instar bloodworms start the construction of U-shaped tubes in the bottom mud. Bloodworms construct them with dirt or silk secreted from the salivary gland of their body.
Note: It was also recorded that bloodworms may occasionally become limnetic (living in the open water), but normally they stay in their tubes until they pupate there.
Bloodworms stay in the lower part of their tubes pumping water periodically by performing undulating movements to provide oxygen for respiration and phytoplankton for food. This stage usually lasts 5-6 days.
The third and fourth instar bloodworms simply increase in size, weight, and generally become darker (dark red). This stage usually lasts 6-8 days.
Under optimal conditions, larval stages last around 2 weeks.
Stage 3: Pupal stage
Bloodworms pupate when they become large enough to transform into adults. It may occur at any hour, day or night, but is most prevalent just before sunset.
This is the shortest stage and generally lasts only a few minutes.
Stage 4: Adult stage (Midge)
Newly emerged midges are already able to fly.
It was assumed for a long time that non-biting midges feed only during the larval stage. As adults, they do not have functional mouthparts. Therefore, the microflora of the midge is established at this stage of the life cycle.
Contrary to former belief, recent studies, has been proven that adult Chironomids can indeed feed on sucrose and glucose. It was found that nutrient intake positively impacts their life cycle by increasing reproduction (in males) and longevity (in females).
For example, males could extend their flight time by an average of 160% over unfed males. Females increased longevity by about 40% which is appropriate to the roles of the sexes.
Definitive identification can be made only by microscopic examination. However, in many species, males can be identified by the presence of exceptionally large genitalia located at the tip of their abdomen. In addition, males are a little bit bigger than females.
For reproduction, midges have a swarming behavior. Males form a dense swarm above the water approximately 1 hour before sunrise and disperse about 1 hour after sunset. Females fly into the swarm for mating.
In many species, males also emerge 2 days before females. It allows females to immediately fly into the male swarm for mating.
Due to individual variations in developing time, swarming may take between 15 and 30 days. During this period, eggs are produced continuously.
After mating, females are ready for oviposition in 20-30 hours. Ovigorous females extrude the egg masses onto their hind legs to easily place them in the water.
Adults generally live for 3–14 days.
Interesting fact: In some species, light intensity, surface color, and reflection beneath the swarm trigger the swarming behavior, which is plausible given the muddy water where they are likely to be found in the wild.
Bloodworms as Live Food
In the aquarium hobby, bloodworms have an important position in the aquatic food chain, being a major food source for fish, crabs, crayfish, and other vertebrates and invertebrates.
According to the study, bloodworms contain lots of protein with a large amount of vitamins and essential amino acids, making it a healthy and nutritious food option for your fish and other tank inhabitants.
|Components||Fresh weight (%)||Dry weight (%)|
|Water||87.9 ± 0.26||–|
|Crude protein||7.6 ± 0.29||55.7 ± 0.28|
|Crude fat||1.3 ± 0.18||9.7 ± 0.3|
|N-free extractive substances||2.1 ± 0.64||26.4 ± 0.48|
|Ash||1.1 ± 0.25||8.2 ± 0.36|
|Arginine||0.29± 0.008||2.12± 0.003|
|Histidine||0.14 ± 0.005||1.02 ± 0.003|
|Isoleucine||0.27 ± 0.010||1.98 ± 0.005|
|Leucine||0.34± 0.005||2.49± 0.005|
|Valine||0.27± 0.009||1.99± 0.003|
|Lysine||0.33 ± 0.006||.48 ± 0.003|
|Phenylalanine||0.37± 0.008||2.76 ± 0.004|
|Methionine||0.30 ± 0.007||2.19± 0.004|
|Threonine||0.27 ± 0.008||2.01 ± 0.003|
|Tryptophan||0.19± 0.006||1.39± 0.004|
Although commercial foods tend to mimic the natural food of our pets (including the essential amino acids), results have also shown that even bloodworms’ partial replacement treatment surpasses them. Feeding your tank critters with bloodworms will help keep them active, healthy, and well-nourished.
Therefore, many aquarists prefer and recommend natural food for fish, crab, and crayfish diets, especially in The main advantages of natural live food compared to the commercial ones are:
- High digestibility (particularly of proteins),
- High water content (85 – 95%),
- Soft and elastic food structure for better ingestion,
- The activity of the food allows animals to react to its
- Less contamination. Unconsumed commercial foods often have high dry matter content, that contaminates water way faster, compared to live
Supplies for Culturing Bloodworms Indoors
The following supplies are needed to culture Bloodworms.
- Starter culture: Egg masses (cocoons) of bloodworm
- Culture vessel: Small tank or plastic container.
- Substrate: Coconut fibre.
- Oxygen: Air stone.
- Harvesting: Fish net
- Maintenance: Dechlorinated water.
- Optional: Jar, cotton swabs, turkey baster, or pipette.
- Food: Animal manure (such as horse manure, chicken manure, fish poop, etc.)
|Even though the adults can mate in an enclosure such as a screen-covered aquarium, culturing bloodworms indoors is not optimal.
For mass production, bloodworms are cultured outdoors in ponds.
Basic Set Up for Bloodworms Culture
- Add the substrate into the tank. There is no need to put a lot of substrate. It will be enough to have 1 inch (2.5 cm) deep.
- Add some conditioned water and mix it with the substrate.
Note: You can also a water conditioner. Let it age for 24 hours to remove chlorine.
- Wait for 1 hour of settling time. It should be enough to produce a substrate layer about 1 inch (2.5 cm) thick.
- Add more conditioned water to create a 1 – 2 inches (2.5 – 5 cm) clear layer over the substrate.
- If your water becomes cloudy, allow time for it to resettle.
- Add some animal manure to the water.
- Gently add egg masses on the surface of the
- Turn on an air stone.
- Place the tank near the window or turn on the lights to maintain a photoperiod of up to 10-12 hours daily.
- Cover your tank to keep mosquitos out.
- Optimal temperature: 72 – 77°F (22 – 25°С)
- Humidity: 60 – 80%
- pH: 0 – 8.0
- Dissolved oxygen: 3 – 4 mg/L
- Photoperiod: 8-12 hours daily.
Large tanks are not needed for indoor culture as they proved to be much less productive per unit area. Tanks as small as 1 to 10 gallons (4 – 40 liters) can be used effectively.
Effect of temperature on Bloodworms
Temperature is a main environmental factor that affects many biological processes in bloodworms.
With an increase in temperature, the duration of stages is noticeably reduced, but at the same time, their death rate significantly increases up to (50-75% at 82 °F (28 °C)). In addition, the fully grown fourth instar larvae cultured at high temperature is small, about half of the size of those cultured at other temperatures at 68°F (20 °C).
Oxygen and Aeration:
The culture water should be aerated continuously using air stones. At the same time, keep the aeration as low as possible to avoid keeping substrate and/or added food in suspension. You can do it by suspending an air stone at a level just below the surface of the water.
When in a low–oxygen environment, bloodworms turn dark red. In their natural conditions, the amount of oxygen rarely reaches 3 mg/l but we do not need that. On the contrary, we need to maximize the oxygen input and thus increasing the developmental rate.
Keep in mind that Chironomidae oviposition habitat preferred quieter than agitated habitat.
Bloodworms are commonly found in slow or still waters because of their poor ability to swim against the current.
Depending on the stage, bloodworms react differently to light.
In the 1st and beginning of 2nd stages of development, positive phototaxis is found in bloodworms. Basically, they are attracted to light.
However, with the appearance of hemoglobin in the fluids, the reaction to light becomes negative. Bloodworms start actively avoiding bright places.
The negative reaction to light disappears in bloodworms at the stage of transformation of the pupa into a mosquito.
Nonetheless, it is still recommended to have a photoperiod of up to 10-12 hours daily, especially, if you have green algae in the tank. Bloodworms will consume these algae.
In aquarium settings, coconut fiber will be probably the best option. Its complex structures are able to capture the organic material in the water and provide a good microhabitat for bloodworms.
In laboratory experiments, bloodworms are often cultured using sediment composed of nettle powder or cellulose from which larvae can directly feed. Using sand as a substrate is not recommended because it may erode the larvae’s mouth parts.
Interestingly, according to the study, bloodworms were found to enjoy a substrate of paper towels.
Note: Shredded paper hand towels were used as the substrate of choice for bloodworm culture. Only a small amount of paper towel shreds adequate to cover the bottom of the aquarium was sufficient to initiate the culture.
- soak shredded paper hand towels in acetone (for at least 30 minutes) to remove impurities,
- rinse in distilled water 4 or 5 times (until the strong odor of acetone is removed),
- boil the paper in distilled water for 1 hour or until most of the color is removed
- cut or tear the towels into smaller pieces and shred them to a coarse pulp using a blender.
Experiments have shown that food level has a very significant influence on the growth and reproduction of bloodworms.
Organic matter is the predominant natural food source of bloodworms.
In their natural conditions, they are usually found in organically enriched waters where they feed on algae, scraps, and associated microorganisms, macrogametes, wood scraps, etc. Basically, their feeding behavior is mostly nonselective.
In the aquarium, bloodworms will benefit the most from:
- animal manure (cow, poultry, pig, chicken, etc.),
- palm oil waste,
- fish food (such as Tetramin).
How much to feed Bloodworms
The daily diet of bloodworms varies within 100-600% of their body weight. The main downside of this method is that it can be hard to calculate in any setup. Thus, nobody does such calculations.
Another way is to provide food at the rate of:
- 5 g/gal (2.5 g/L) for dried animal manure or
- 110 g/gal (30 g/L) for fresh animal manure.
Generally, the use of dried solid waste produces higher bloodworm biomass compared to the use of fresh solid waste and improves the survival rate in all larval phases up to 90%.
How to feed Bloodworms
Liquified food is highly recommended because it is uniformly distributed in the culture.
Food can be prepared by blending it with distilled or carbon-filtered water. Extra food can be kept refrigerated. Warm up refrigerated food and shake the mixture well before usage.
How often to feed Bloodworms
Regardless of sediment type, feeding is necessary for the cultures started with first-instar larvae. Therefore, add some food right at the start of each culture.
After that, feed bloodworms after every change of water (every 3-4 days).
If too much food has been added, the water will become cloudy the next day. In this case, water should be replaced immediately to prevent contamination.
Maintenance of Bloodworms
Once initiated, the bloodworm cultures require very little maintenance. Under optimal conditions, it will produce an abundant supply of bloodworms.
Water changes must be done every 3-4 days due to the fact that the amount of food may significantly affect water quality.
Surface water should be siphoned off down to a level just above the substrate. Add new water until the original depth is reached.
In most species, the bloodworms can be harvested after 14 days when they reach 0.5 – 1 inch (10 – 25 mm) in length.
However, when the first pupae are observed, they should be harvested immediately.
- Use the smallest mesh-size fish net you can find. Ideally, the mesh size should be around 1×1 mm.
- Scoop and rinsed under tap water to wash away all the waste.
Live bloodworms can be stored in a variety of ways. The easiest way is to place them in a damp rag at the bottom of the refrigerator. A slightly damp bloodworm can be also placed in a tightly covered container.
The bloodworm should be placed in a thin layer (no more than 0.4 inches or 1 cm).
By using these methods, it is possible to store bloodworms for at least 2-3 weeks.
How do I feed fish, crabs, and crayfish frozen bloodworms?
If you are going to feed your critters frozen bloodworms DO NOT drop a whole cube in at a time. You need to thaw it. Put the cube in a net under a stream of cold tap water. The liquid contents should be drained away. Then feed it to your pets.
Is it safe to feed animals with bloodworms?
The answer depends on the conditions where bloodworms were cultured.
The natural waters in which they were collected can contain diseases and parasites. Thus, bloodworms may carry them in their body tissues. However, bloodworms cultured in treated water are much less likely to carry pathogens.
Unfortunately, there are no reliable ways to find out where and how bloodworms were collected/cultured. Therefore, the risk of introducing pathogenic microorganisms into the tank along with living food remains, and we should always remember this.
Do bloodworms (Chironomid) bite?
Bloodworms (Chironomid larvae) do not bite. They are neither carnivorous nor poisonous. They simply do not have any means to attack.
Where Can You Get Live Bloodworms?
Although it is possible to find them near water bodies, they may also carry diseases. Therefore, if you want to culture them, I would recommend finding someone that already has a clean culture. Play safe.
In all other cases, simply get bloodworms in pet stores.
Freeze Dried Blood Worms – link to check the price on Amazon
Rearing of bloodworms is possible but problematic because of their dual mode of life in water and in the terrestrial environment. Generally, it is only worth doing on a big scale.
Therefore, unless you are doing it as a personal challenge to prove your skill sets, or out of curiosity, I would just recommend buying bloodworms instead of culturing them.
|Bloodworms as Live food|
|Incredibly high nutrient content||More expensive than commercial foods|
|Contain lots of vitamin and mineral supplements||Potential for disease transmission|
|High digestibility||Live foods may only last a few days or weeks.|
|Culturing them indoors (full cycle from larvae to midges) is problematic because of their dual mode of life in water and in the terrestrial environment|
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