What Are Bloodworms? (Where They Come From & What They’re For)

Last Updated on 2023-08-12

If you keep tropical fish or frequently go freshwater fishing, you might be familiar with bloodworms. If not, you might be wondering, ‘what is a bloodworm?’ and what are they used for?

The name ‘bloodworm’ certainly has some connotations, and their appearance is probably precisely what you are expecting. Bloodworms are bright red in color and can be found in soft ground and freshwater. They can grow up to 14 inches long, and they are carnivorous.

If you are looking to feed bloodworms to fish, you don’t want to buy them at their full size, especially if you keep smaller fish who might not know what to do with large, live bloodworms.

Bloodworms can be found in most regular pet stores, thanks to the fact they’re a great source of food for fish! They can be bought live, frozen, or freeze-dried, and there are pros and cons to each type of bloodworm.

This article will look at some surprising facts about bloodworms and consider whether you should be feeding them to your fish. Some risks come with these nutrient-dense worms, and you must understand these when looking to add bloodworms to your fish’s diet.

So, What Exactly Are Bloodworms?

Undeniably, bloodworms are rather strange-looking, and it’s natural to wonder where such things came from. Bloodworms are a type of larvae that eventually mature into flies. They are the larvae of the non-biting midge fly and are a type of annelid, which means segmented worm.

‘Bloodworm’ is an umbrella term for various worms, but their bright red color characterizes them all. The Latin name is Glycera dibranchiata, and they are a group of bristle worms that are found in shallow waters. Bloodworms are this vivid red color due to the iron-porphyrin protein in their blood and tissue.

Bloodworms are pretty much at the bottom of the aquatic food chain; most fish would eat bloodworms if given the opportunity. They can be used to feed pet fish, but they are also enjoyed by frogs, crabs, shrimps, snails, and even salamanders and turtles.

Where Do Bloodworms Come From?

Bloodworms are typically found on the Northeast coast of America. They live in freshwater pools and ponds, but they also do well in polluted water with low oxygen levels due to their high hemoglobin content. 

Maine, New Jersey, and Connecticut are known for having bloodworms along their coasts, and if you are buying bloodworms, this is most likely where they originated.

They can be found around muddy coastlines during a low tide. You might find them on the underside of rocks in muddy areas. They are most likely to be found in the benthic zone and in areas where the ground is soft enough for them to burrow into. However, they can be found down to depths of 24 meters (79 feet) or more.

Close up very many small slippery red mosquito larvae moths on white background. Perfect fishing bait.

Types of Bloodworms

If you’ve kept fish for a little while, you will have no doubt heard about bloodworms and the different forms in which you can buy them. They each have their advantages, depending on what you what bloodworms for. You can buy bloodworms live, frozen, or freeze-dried.

Live Bloodworms 

Some people tend to prefer buying live bloodworms as they think that this Is the freshest way that they can give their fish food. There is some truth in this; live bloodworms are absolutely fresher than frozen or freeze-dried varieties.

Live bloodworms are dense in nutrients and vitamins compared to the other forms. Your fish will feel the benefits of live bloodworms. If you are thinking of breeding your fish soon, giving them live bloodworms is an excellent way of providing a nutrient-rich diet for them in preparation.

Feeding your fish live bloodworms will most likely make them seem quite active, whereas frozen or freeze-dried bloodworms might not have this same effect. 

However, as you might have guessed, live bloodworms can’t be stored for nearly as long as frozen or freeze-dried types. Once they have been purchased, you have about 2-3 days where you can feed your fish live bloodworms before the bloodworms die, and they will no longer be able to be fed to fish.

Fresh bloodworms also come with a larger risk of illness for the fish eating them. If you are feeding your fish bloodworms for the first time, keep a close eye on them afterward and only give them a small amount,2 to begin with. Be sure that you are buying your bloodworms from a trustworthy business to minimize the likelihood of the live bloodworms being diseased.

Frozen Bloodworms

Frozen bloodworms are the type used most commonly by those looking to add extra nutrients to their fish’s diets. They are a lot more convenient to buy and store, as they can be kept in a freezer for up to six months, meaning you can take out a portion to feed your fish as and when you need it.

Freezing bloodworms also hugely minimizes the risk of them being diseased and making your fish ill. If you have never fed your fish bloodworms before, this might be the type to go for, as they don’t really require any prep, and you don’t need to worry about them making your fish ill. 

Frozen bloodworms also mean you can control the portions you are giving your fish a little more. The bloodworms can be spread throughout the aquarium evenly, giving all of your fish a chance to eat them, rather than fresh bloodworms, which risk being eaten by just one of your fish. 

However, frozen bloodworms will not cause the same frenzy among your fish as live bloodworms will. Some of the nutrients may have been lost, though they are still packed with the right things that fish require. 

You do still need to wait until your frozen worms defrost before you can feed them to your fish. This takes a little bit of planning, as you will need to get the right amount out of the freezer a couple of hours before your fish’s usual dinner time.

Also, getting the portions right for tour fish with frozen bloodworms is essential. There is a risk of them disrupting the filter process as it is unlikely that all the bloodworms will be eaten. If you are newly introducing bloodworms to your tank, perhaps add less than you think to see how your fish react to them before disrupting life in the tank.

Freeze-Dried Bloodworms

Freeze-dried bloodworms are another great option if you are looking for a convenient way to get bloodworms into your fish’s diets. They do not require any prep or defrosting time, and you can control the portions that you are giving really easily. If you don’t want to spend much on bloodworms, freeze-dried is the cheapest way to buy them.

You can buy different quality grades of freeze-dried bloodworms, so be sure to read the label of the bloodworms you are buying. It might be that the cheap option looks great, but in reality, it might not provide any of the benefits that are expected of bloodworms. Investing more, in this case, is probably worthwhile.

Freeze-dried bloodworms are definitely the least healthy and nutrient-dense option for your fish. Your fish will not get as excited about these as live bloodworms either, and you probably won’t see a change in their behavior as you might when giving them fresh ones.

Though they do not require any prep time, if your fish spend most of their time at the bottom of the tank, you will have to wait for the freeze-dried bloodworms to absorb some water in order to sink to the bottom of the tank.

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Uses of Bloodworms 

Since fish enjoy bloodworms so much, they are often used as fishing bait or to feed aquarium fish. Their meaty texture is enjoyed by big predatory fish, making them really popular on the fisherman market.

Depending on the size of your fish, bloodworms make for great food in aquariums. If your fish are small, you will not want fully grown 14-inch bloodworms, but the younger ones will be enjoyed in your tank at home.

Bloodworms can act as a laxative for fish, so if you think your fish might be constipated, feeding them bloodworms will help their digestive systems return to normal. Too many bloodworms can constipate them again, however, so don’t try to feed them bloodworms every day to solve this issue.

If your fish do not seem to be enjoying their current food, bloodworms can be used to perk them up. Live bloodworms especially will cause a hive of activity in your fish tank, and the iron and protein found in bloodworms should give your fish a boost of energy.

Who Eats Bloodworms 

As mentioned briefly above, bloodworms are pretty low in the aquatic food chain. Pretty much any fish will eat bloodworms, including both saltwater and freshwater fish. The fish you keep in a tank will most likely love bloodworms and will benefit from the nutrients they contain, too.

The fish that will undoubtedly enjoy bloodworms include:

Platy fish

Discus fish


Kuhli loaches

Betta fish

African cichlids


However, all kinds of fish (except strict herbivores) will enjoy eating bloodworms, so you’re unlikely to waste your money by buying some to try in your tank.


Are Bloodworms Harmful to Humans? 

Though they are relatively low in the food chain, humans should be a little wary around bloodworms. They are carnivorous, and when hunting for prey, they will extend a long proboscis from their heads and will bite. They can release venom, which should not harm a human since it will be in a small quantity, but its bite will hurt a little. Those who have experienced it compare it to being stung by a bee; painful but bearable.

If you are looking for bloodworms in the wild or handling live ones to feed to fish, it is recommended that you wear gloves. This will keep you safe from any bacteria that may be on the bloodworms and prevent you from being hurt if the bloodworms decide to bite.

Can I Breed My Bloodworms?

Breeding your bloodworms might seem like the perfect solution to the problem of obtaining fresh bloodworms and having them in regular supply. To be able to reproduce bloodworms, you need somewhere for them to mature into flies. However, adult flies tend to want to lay their eggs elsewhere and will try to fly away.  Raising bloodworms from eggs is more straightforward; click here to find out more about that.

How Often Should I Feed My Fish Bloodworms?

Though bloodworms are good for fish, it is vital to feed your fish a varied diet. Bloodworms do not have all of the vitamins fish require to thrive. They contain high quantities of protein and iron but not much else. Therefore, you should aim to feed your fish bloodworms once or twice a week. Bloodworms tend to act as a laxative for fish, but too many bloodworms can constipate your fish, too. It’s all about balance.


Bloodworms are a healthy addition to your fish’s diets, and the most nutritious bloodworms you can feed your fish are the live, fresh variety. If you’re not able to get your hands on these, frozen or freeze-dried bloodworms are available.

You can look for bloodworms in the wild yourself, especially if you live on the Northeast coast of the United States. They can be found in freshwater ponds or pools, near soft sand, and often under rocks. They can bite, so if you are handling live bloodworms, gloves are recommended.

Any pet fish are likely to enjoy bloodworms, and you will notice your fish becoming lively and excited if you choose to give them live bloodworms, which are fun to watch. The protein and iron present in bloodworms make them a great addition to the food you are already giving your fish; however, they should be part of a healthy diet and given in combination with other food sources to ensure your fish can get all of the nutrients required to thrive.

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