Detritus Worms in Freshwater Tank

Detritus Worms in Freshwater Tank

Getting to see uninvited critters and harmful parasites in a fish or shrimp tank is something no aquarist hopes to experience, the mere thought of such occurrence is quite annoying.  However, the lack of knowledge can play a very negative role here as well because not all worms in freshwater tanks are bad.

Detritus worms are pretty common in aquariums, so there is no need to stress out. Even more, they are quite beneficial and unproblematic when present in small numbers. In addition, these little scavengers do not cause harm to tank inhabitants.

In this article, I will be looking at the profile of detritus worms, what they are, how they get in our tanks, in addition to effective measures geared towards controlling their population.

What are Detritus Worms?

In case you’re wondering what detritus worms are, these are a family of oligochaete worms called Naididae. Being annelids implies that they are close relatives to species like earthworms and they share similar physical features and reproductive capacities (hermaphroditism).

Detritus worms are hermaphroditic which means that they have both male and female reproductive organs.

The Naididae family comprises about 800 species. Therefore, it is not possible for an ordinary hobbyist to find out what exact species they have in the tanks. Luckily we do not need that. All we need to know is that they are detritus worms (not pest worms) and it can be done pretty easily.

How to Identify Detritus Worms

Detritus Worms in Freshwater Tank descriptionDetritus worms can be identified by their form —existing as thin, white, wiggly worms in the fish tank. When viewed from a distance, they look like long, tiny pieces of white strings or threads.

These worms have thin segmented bodies and white coloration. They move by crawling on the substrate in a fashion similar to that of earthworms or by quickly wriggling (snake-like movements) when swimming.

These worms are considerably small, with the size ranging from a millimeter to few centimeters long (up to 1 inch but usually from 0.1 to 0.5 inches), and they can be seen lying on the substrate, swimming freely in the water column or latching onto the tank walls.

Detritus worms become more active when it is dark. During the daytime, they usually burrow in the substrate or hide under driftwood, rocks, etc.

Behavior of Detritus Worms

Detritus worms reside and breed in the substrate and even filter media where they equally gain access to leftover food, debris, and decomposing organic matter. They are detritivores, hence it’s obligatory for them to feed on accumulated waste material in the aquarium.

| Detritus worms eat only decomposing organic (plant and animal waste) material.

Notably, when oxygen level depletes significantly at the bottom, detritus worms will migrate from the aquarium substrate (gravel) towards the water surface to access higher levels of dissolved oxygen needed for their sustenance, thus it’s normal to see them floating in the water column.

How do We Get Detritus Worms in our Tanks?

Detritus Worms in Freshwater Tank in the substrateDetritus worms are present in many aquariums, and their means of introduction is usually through new aquarium fish or live plants. They are excellent hitchhikers, so, it is very easy to accidentally introduce them into the tank. 

They often make their way into aquariums by clinging tightly to live plants and fish, that’s why it is crucial to disinfect or quarantine new arrivals before introducing them into the aquarium. In some cases, they exist abundantly in aquarium substrate obtained from another tank.

Poor water quality and overfeeding are other reasons why they get into our tanks.

Once detritus worms are in the tank, they make themselves at home easily. Many experienced aquarists accepted them as a natural part of the hobby.

So, if you are running your tank for a year or more it is very likely that you have a detritus worm colony in the tank. Maybe you do not know about it yet. 🙂

Main causes of Detritus worms:

  • Hitchhiking.
  • Bad water quality.
  • Poor maintenance.
  • Overfeeding.

Are Detritus Worms Dangerous to Shrimp, Fish, and Snails?

Detritus Worms in Freshwater Tank on the glass
Tiny detritus worms on the glass

The good news is that detritus worms are harmless, they won’t cause harm to fish, dwarf shrimp, snails, and other critters in the tank. On the contrary, they can serve as a healthy food source for your aquarium fish and fry.

So, it’s perfectly fine to have a bit of these worms in your aquarium, you should only be bothered when there is overpopulation.

Pros and Cons of Detritus Worms in Freshwater Tanks


  • Clean up crew. These worms will help in keeping the freshwater tank clean by feeding on tiny particles of organic detritus on the bottom of the tank. Detritus worms are beneficial to the ecosystem since they aid in cleaning the aquarium by picking up leftover food and debris for their consumption and breaking down wastes.
  • Live food. They make great food for small fish, fry, frogs, crabs, and crayfish!

  • Unsightly. They do not look pretty.
  • Oxygen depletion. Can cause oxygen depletion when you have way too many detritus worms in the tank. Eventually, the worm population will have to compete with your fish for oxygen. Hence it would be detrimental if there are low levels of dissolved oxygen in the aquarium.

How to Get Rid of Detritus Worms

I know that many beginner aquarists freak out when they see them for the first time. Please, don’t!

These nematodes are a harmless and beneficial part of the ecosystem. Therefore, it’s not advisable to remove all Detritus worms from your tank. You just need to reduce their huge population to prevent possible adverse effects.

How do you know that you have too many?

Detritus worms are in most aquariums, but may never be seen, as they live in the substrate. However, if you see them everywhere – swimming in the water column, sitting on the glass, and sticking out of the substrate, in this case, you should do something about it.

  • Improve Your Maintenance Practices

First of all, you should be keen on your tank hygiene/maintenance practices.

Engaging in regular cleaning of the aquarium gravel using a vacuum cleaner will help eliminate a substantial amount of Detritus worms from the substrate. This activity will equally help remove the plant and animal waste materials, as well as uneaten fish food that these worms ingest constantly.

Vacuuming is a really effective way to remove excess worms from the substrate, in addition to the food they consume.

  • Water Changes

Another necessary step is to perform a water change (up to 50%) to eliminate the population of Detritus worms in the water column.

Note: If you keep shrimp, big, and (or) frequent water changes can cause molting problems.

Just stir the substrate to allow the worms to emerge to the surface, then gently target and siphon them out of the aquarium together with the tank water. Afterward, refill the tank with clean dechlorinated water, and ensure that the tank is properly cleaned from time to time.

  • Stop Overfeeding. Consider Your Schedule

Furthermore, you need to cut back on feeding. Do not overfeed, only serve your aquarium fish enough to be consumed within the shortest time possible, and the fish diet should be one that can be easily digested.

If there is any uneaten food after 10 minutes, remove it so that the worms won’t gobble it down. For the shrimp tank, you can leave it for 2 – 3 hours before removing leftovers.

You can read more in my article “How Often and How Much to Feed Shrimp”.

Feeding your animals less translates to less waste been produced, which will help in preserving the water quality and indirectly cutting off the food supply to the worms so they don’t flourish.

  • Overstocking

Also, watch your bioload, overstocking your tank with fish and invertebrates will increase the production of excess waste which ruins the water and improves the living condition of detritus worms.

  • Filtration

Filtration is another factor that can impact the growth of detritus worms in aquariums. So, check your filtration system for any issues.

Population explosion would easily occur in tanks with poor filtration, poor water quality, and increased decomposing mulm. The aquarium needs a capable and efficient filtration system (mechanical and bio filtration) to deal with the wastes and pollutants.

Having good filtration and sufficient water movement in your tank will help improve water quality and also increase the level of dissolved oxygen in the tank water.

  • Chemical Removal

The first thing I should mention is that I really do NOT recommend using it against these worms. Using medications to kill off detritus worms is a horrible practice.

There is no need in employing toxic chemicals to treat a detritus worm problem, the use of medications such as:

  • No-Planaria,
  • Fenbendazole (Panacur and Canine Dewormer),
  • PraziPro,
  • AAP Dyacide, etc.

can have good initial results with bad consequences. So why is that you may ask?

The point is that during and after treatment, many detritus worms will be in the substrate. So, they will die there. As a result, over the course of like one or two weeks, they will basically rot in the substrate with the massive amount of ammonia that comes with it (it can kill your fish or shrimp.). 

So, killing too many at once can be very dangerous for the tank eco-system. If you are still persistent with your decision – at least vacuum the substrate!

To know the safe dosages, you can read my article “Planaria and Shrimps. How to remove them”. You will find detailed descriptions and step-by-step algorithm.

Reducing the detritus worm population is the best practice.
Simply carry out proper tank cleaning practices, lower your bioload, avoid overfeeding, and ensure that good filtration occurs in your aquarium.
  • Biological Removal

Of course, there are some fish species (also crayfish, crabs, and frogs) that will eat detritus worms. In some cases, they will go crazy for them, for example:

Warning: Unfortunately, these fish can also become a problem for shrimplets.

Of course, you can try some small fish fry (like guppies), but eventually, you will have to move them elsewhere if you do not want them to pose a continued risk to your shrimp.

Keep in mind that big fish usually do not show any interest in eating detritus worms.

CO2 and Temperature Trick

Some aquarists gassed the tank with enough CO2 to completely deplete the oxygen levels. It forced detritus worms to get out from the substrate and swim for oxygen. This way it becomes way easier to siphon them up from the water column.

These worms don’t like warm temperatures. Therefore, increasing it by 15+ degrees will also shock them.

The problem though is that both these methods can harm livestock in the tank.  

Differences between Detritus worms, Camallanus Worms, and Planaria

Aquarists often use the term detritus worm when they do not know the scientific name since there are so many different species. As a result, it only creates more confusion and misunderstanding.

Planaria Worms

Detritus Worms in Freshwater Tank - Differences between Detritus worms, and Planaria

Planaria are quite different from Detritus worms.

Planaria have flattened bodies, with a spade-shaped head and two eyespots present, and they exist in lesser numbers than detritus worms which tend to proliferate more easily. Also, Planaria usually attaches and crawls swiftly on the tank glass.

Planaria are capable of both asexual and sexual reproduction, and they possess extraordinary regenerative abilities. For instance, cutting a single worm into several pieces will give rise to whole new individuals after a while.

In addition, these are carnivores and scavengers, known to consume insect larvae, dead or living small fish, and inverts. Planaria worms are dreaded in fish and shrimp tanks because they can inflict injuries on shrimp and the body parts of lethargic or slow-moving fish, they can also harm and/or devour fish eggs.

Camallanus worms

Detritus Worms in Freshwater Tank - Differences between Detritus worms and Camallanus Worms
Camallanus Worms

Camallanus worms are very thin and small. They look like pink threads and are only a few millimeters long. These worms live in the intestines of a fish where they attach themselves and feed off of the host’s blood.

In most cases, you will not see an adult Camallanus worm outside of a host. They protrude from of the rear end of the infected fish.

Unlike Detritus worms, Planaria and Camallanus worms deserve no place in aquariums, hence they should be removed completely.

  Camallanus Worms Planaria Detritus worms
Habitat Fresh and saltwater Fresh and saltwater Fresh and saltwater
Aggression Internal, parasitic


External, parasitic nematodes Harmless
Body structure Thread-like pink worms Flat and thick Thread-like white worms
Head structure They have an arrow-shaped head.
Feeding Carnivorous  Carnivorous  Detritivores 
Mouth features They have a ‘mouth’ in the middle of the body on the underside
Movements Move slowly (more of a gliding) Fast, snake-like
Swimming Only during the larva stage Do not swim Can Swim
Reproduction rate Slow Slow Fast reproduction

In Conclusion

Regardless of how you look at it, detritus worms are not a foe to aquarium setups. Through their daily activities, these worms contribute positively to the tank’s cleanliness and that’s commendable.

A surge in population is usually the problem, hence the need for a significant reduction in their mass through thorough substrate vacuuming and water changes. Some go as far as changing the entire substrate, but that would mean letting go of the beneficial bacteria formed therein.

By engaging in proper cleaning and maintenance practices, cutting back on feeding, and keeping to proper feeding and stocking levels, the worm population will remain normal.

As for planaria and camallanus worms, the tank’s hygiene has no part in its proliferation, so you have to face them squarely— treating the tank water with a good worm medication is definitely the way to go.

6 thoughts on “Detritus Worms in Freshwater Tank

  1. I would like to say that i have found detritus worms many times. There are currently many living in my infusoria culture, a few in my now empty but will-be shrimp tank, and sometimes a few in my fish tank.
    I will note that my corydora fry showed no interest in eating one that was wiggling around in the water column, but its possible it got eaten when it landed.
    I am a fan, keep up the great work!

    1. Hi Fred,
      Thank you for your kind words and for providing the feedback.
      It is strange that your Corydoras fish aren’t particularly fond of detritus worms, but it’s certainly plausible. After all, every individual – including fish – has their own unique preferences and tastes.
      Best regards,

  2. Literally what do I treat with? Thanks for the article identifying the issue that I already identified to be able to Google. Now what’s the fix?????

    1. Hi Sabrina,
      I’m not entirely sure what specific question you have, as I have addressed the topic of dealing with these worms in the aquarium in a significant portion of the article.
      Best regards,

  3. oh help I had a second aquarium with 4 shrimps and 3 snails the snails gave birth and made about 50 eggs after a while the aquarium was full of worms I decided to change them to my other aquarium where I have about 11 fish everything was fine for a few days until many worms spread again in this aquarium and unfortunately all these snails gave birth again, I don’t know what to do😭😭

    1. Hi ξενια,
      Do you want to get rid of snails? worms? both?
      Best regards,

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