What Are The Brown Worms In Your Fish Tank? (& Why They’re There)

When it comes to fish tanks, gaining an understanding of what is normal and what is not normal requires a significant investment of time and effort. There is a lot of gray area between the two of them. Worms absolutely need to be added to that list. Are they dangerous to my fish or the environment where they live?

Worms are not always a bad thing; depending on how everything is set up, they may even be a natural part of the ecosystem that exists within your fish aquarium. Sometimes they’re nothing to worry about, but other times they indicate a serious issue with your tank’s health. These worms are a tasty treat for fish, and there are some species of fish that actively search for them to consume.

On the other hand, if there is an abundance of food in the tank, the population can rapidly increase, and the aquarium will start to look like a worm farm. Many people find themselves dealing with this issue. But what are these worms, and why are they in your fish tank? Keep on reading to know more about the different types of brown worms that can invade your tank, as well as how to get rid of them.

What Are The Tiny Brown Worms In Your Fish Tank?

Tiny brown worms are a common nuisance in freshwater tanks. These pests can be difficult to control and eliminate, but it is important to do so to maintain the health of your fish and plants. There are several different types of tiny brown worms, each with its own unique characteristics.

Some of the most common types of tiny brown worms include:

Detritus Worms

They have the appearance of stringy, pointy, white-brown filaments that wriggle through the water and in between the pebbles. Detritus worms are detritivores, which means that the only food they consume is dead plant and animal matter that has decomposed. These types of worms can have a negative impact on the health of your fish, as they can cause blockages in the intestines that may lead to death.

Planaria (Dugesia

Aquarists generally view planaria, a type of flatworm, as an undesirable intruder. These flatworms can breed rapidly, posing a threat to the other inhabitants in your aquarium. Planaria can be easily recognized by their arrow-shaped heads, which can be seen without a microscope. It’s unfortunate that this form isn’t always readily apparent due to planaria’s tendency to compress.

Anchor Worms

In contrast to other parasites, anchor worms are macroscopic and thus visible to the naked eye. These worms live on the bodies of fish and feed off their blood. Anchor worms may not be visible until they have attached to a fish but can often be found around inflamed areas where they have recently been feeding. They are most frequently seen on koi and goldfish but can appear on any kind of freshwater fish. The part of the fish that looks like a “worm” and sticks out into the water is actually the female reproductive organ.

Camallanus Worms

The camallanus worm is a typical parasite of the digestive tract of tropical fish. A rasping organ at the nematode’s front end is used to drill into fish flesh and draw out their blood for consumption. The organ also serves as a secure base. A frequent symptom of worm infection in fish is the presence of the worm’s tail hanging out of the anus. As it drains blood from the fish, it will change color.

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Why Are There Little Brown Worms In My Fish Tank?

There are many possible reasons why little brown worms might be in your fish tank, and it is important to determine the specific reason for the outbreak of these pests so that you can take steps to prevent them from attacking your fish in the future. Some of the most common reasons include the following:

  • Improper tank maintenance – Regularly cleaning and maintaining your fish tank is essential for ensuring that it doesn’t become overrun with unwanted pests like these worms. It’s important to remove any uneaten food or waste that has accumulated in the bottom of the tank as it can attract unwanted organisms like these worms.
  • Overfeeding –  If you are not careful about how much food you give to your fish, it can result in excessive nutrient accumulation in the water. This, in turn, can lead to a proliferation of brown worms and other unwanted pests. To prevent this from happening, it is important to limit the amount of food that you provide your fish and monitor their feeding behavior closely. 
  • Poor water quality – Another reason why brown worms may be present in your fish tank is poor water quality, which can occur if you don’t change or clean the aquarium water frequently enough. Dirty or poorly oxygenated water provides a perfect breeding ground for these worms, so it is important to check the water quality regularly and make any necessary changes.
  • Presence of other pests – In some cases, brown worms may be present in your fish tank as a result of an infestation of another type of pest. Examples include snails, algae, or flatworms, all of which can leave behind debris that attracts brown worms. If you notice an infestation of any other type of pest, it is important to remove them promptly and take steps to prevent future infestations.
  • Poor fish health – It can also be a contributing factor to the presence of brown worms in your fish tank. If your fish are stressed or undernourished, they may be more susceptible to certain parasites and diseases that could lead to the presence of brown worms. To prevent this from happening, it is important to keep your fish healthy by feeding them a high-quality diet, providing appropriate habitat conditions, and performing routine check-ups on their health.
  • New fish – In some cases, brown worms may simply be present in your fish tank due to the introduction of new or recently purchased fish. As these newly introduced animals acclimate to their environment, they may bring along any parasites or pests that were already present in their own aquariums. To prevent this from happening, it is important to quarantine new fish for a period of time before adding them to your main fish tank.

You can help keep your fish tank free of brown worms and other pests by being aware of the potential causes of these problems and taking steps to prevent them from occurring.

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How To Get Rid Of Brown Worms In Your Fish Tank

Worms have a rapid life cycle that includes both rapid development and rapid reproduction. Brown worms are notoriously difficult to eradicate from an aquarium because they feed almost exclusively on decaying organic matter. Infestations of brown worms can be challenging to eliminate, but there are several things you can do, including the following:

Cut Down on Feeding

The most crucial step in permanently eliminating brown worms is reducing feeding frequency. If your fish don’t consume all the food, you should promptly remove it, perhaps with a siphon. This ought to ward off a further brown worm invasion and aid in the ongoing fight against the current one. Because an abundance of food might cause ammonia increases, this is also beneficial for the aquarium’s overall health.


Infestations of brown worms can be challenging to eradicate without resorting to chemical treatments. Cutting back on feeding is the first step; once you’ve done that, you can try removing them on a regular basis with a siphon or a trap. Population decline should be accelerated by this measure.


Before you dispose of them, it is recommended that you first put them to death by boiling them or by freezing them solid. You really shouldn’t try to crush them by hand, despite how tempting it might be. This is because some worms are asexual, which means that they are able to reproduce even when they are cut up into smaller pieces.

Change the Water and Other Objects

If you suspect brown worms or realize an infection has taken place, you should immediately change out the tank water. After draining the tank, fill it with clean water that has undergone a purification process. If the fish are severely impacted by the worms, they should be quarantined. Every 3–4 days, you should check in to see how things are going and replace the water.

Use Gravel Vacuum

Brown worms in an aquarium can be fed by the leftover food in the tank. Do not hesitate to use a gravel vacuum to get rid of any stray morsels of food from the fish tank. Without draining the tank, you can use a gravel vacuum to get rid of stale food and worm waste.

Upgrade the Filtration in Your Aquarium

It is recommended that you upgrade your filtration system in order to maintain a healthy pH and oxygen level. Mechanical filters can be used in this situation because they are clean and simple to keep up. Additionally, it aids in stopping the development and spread of brown worms. Worms can enter your aquarium through the feed, so be careful.

Potassium Permanganate Solution

Worm eggs are more difficult to find and more challenging to eradicate. However, if you think they might be there because of the fish’s growing conditions, you can kill many eggs and adult worms with a 24-hour soak in a solution of potassium permanganate. This should be the very last option.

If you are determined to get rid of the brown worms in your fish tank, there are a few methods that you can try. The easiest way is probably to purchase a commercial worm treatment and follow the directions on the package. You can also try using natural remedies to kill the worms. However, it is important to take care when using these methods, as they can be harmful to both your fish and plants. Finally, you can also manually remove the worms from your tank by hand. Whichever method you choose, make sure to keep an eye on your fish after treatment and monitor their health closely. 

How To Prevent Brown Worms In Your Fish Tank

Many people are eager to have a fish tank and enjoy the beauty of colorful fish swimming around. However, having a fish tank also comes with its share of responsibilities, in particular, taking care of the tank and maintaining proper water quality by regularly cleaning it. Cleaning your fish tank should be done frequently to prevent algae growth or brown worms from appearing in your tank.

There are a few things you can do to prevent brown worms from infesting your fish tank, such as:

  • Keeping the substrate clean. If you have any gravel or other types of substrate in your tank, be sure to clean it thoroughly and regularly. This includes cleaning the areas around any decorations or items in your tank too, removing dead leaves and debris from the top of the substrate – When you perform regular water changes, be sure to also remove any dead leaves or plant
  • Avoid overfeeding your fish. Although it can be tempting to feed your fish as much as possible, resist the urge and make sure to only give them a moderate amount of food at each feeding. This will prevent excess nutrients from entering the tank and contribute to algae growth or brown worm infestation.
  • Ensuring that your tank is not overpopulated. In order for your tank to stay healthy, it’s important that you don’t overcrowd it with too many fish or other organisms. This will create excess waste and make it difficult for the filter and water conditions to remain healthy. By following these tips, you can help keep your tank free from brown worms and maintain clean, clear water quality.
  • Regular water testing.  In addition to this, it is essential to conduct water tests on a consistent basis and monitor the water quality in your tank. This will make it easier for you to recognize any potential problems and take prompt action, preventing brown worms from taking control of your tank in the process.
  • Quarantine new fish. If you do decide to add new fish to your tank, be sure to quarantine them first. This will allow you to closely monitor their behavior and health, which can help spot any signs of illness early on and prevent brown worms from spreading throughout the rest of the tank.
  • Watch out for early signs of fish diseases. It’s important to keep an eye out for other signs of illness in your fish, even if you don’t see any worms in the tank. Consult a vet if you are worried about your fish’s health. There are a few things to keep an eye out for that could mean your fish is sick:
  • Being disoriented
  • Turning upside down or swimming in a goofy pattern
  • Not eating
  • Fish has white spots on their scales or gills
  • Discoloration
  • Difficulty taking a breath, resulting in behaviors like staying near the water’s surface
  • puffy eyes
  • The body is covered in mucus
  • Scratching and scraping against Solids
  • Separating from other fish.
  • Sores
  • Bloating
  • Shape, size, or appearance change

If you notice brown worms in your tank, take immediate action to remove them. You can also use a net to manually remove them from the water or consult with an aquarium professional for other treatment options. By taking these steps and following the other tips mentioned above, you can help keep your fish tank free from brown worms and maintain a healthy environment for your fish.

Where Do The Brown Worms In Your Fish Tank Come From?

Have you ever noticed small, brown worms crawling around in your fish tank? These little guys are actually a common presence in tank water and are usually harmless to both fish and plants. So, where do they come from? The most likely explanation is that they were there all along, hiding in the substrate or decorations you added to the tank. Brown worms can also appear if organic matter, like fish waste or uneaten food, starts to break down in the water. 

In either case, these worms can actually serve as a source of food for some species of fish. That being said, it’s still important to keep an eye on their population and clean out any excess organic build-up from the tank to prevent them from getting out of control. You may also want to consider adding some tank-cleaning snails as natural worm predators. Happy fish-keeping!


Brown worms in your fish tank can be a real nuisance. Not only are they unsightly, but they can also be harmful to your fish if left untreated. Hopefully, armed with this information, you can identify the issue and take corrective action if necessary. Fortunately, there are several ways you can get rid of brown worms and prevent them from coming back. We’ve outlined some simple steps you can take to get rid of these pesky critters and keep your fish healthy and happy. By following the tips in this blog post, you can keep your fish tank healthy and worm-free!

About the author

Hey! I'm Antonio!

Betta fish keeper for over 6 years now! Since owning a betta I've also housed all kinds of tropical fish, and have seen all manner of problems and how to look after them!

If you need any advice you can always message me or better yet join the Facebook group where a community can answer your questions!