Worms in Fish Tank: Types, Identification and Removal

A dirty, smelly tank is a disease causing lair. It is a breeding ground of nefarious looking worms that dominate the ecosystem and are very difficult to remove.

Worms that infest aquariums could harm the fish in various ways. They could infect the gills and fins of fish making it difficult for them to breathe and move. They could also get inside the fish’s body and breed in their intestines causing the fish to bloat, lose appetite, and if left unchecked, eventually die.

If you don’t want your fish to meet such a painful fate, maintain certain precautions and opt for medical treatments at the soonest. This article is the ultimate worm in fish tank guide, identification and removal all in one place.


Different Types Of Worms And How To Identify Them

The method of removal of worms in the fish tank depends upon their identification. You can identify worms based on their shape, their movement, and places they choose to colonize in the fish tank.


1. Detritus Or Annelid Worms

They belong to the group Annelida or segmented worms. They resemble earthworms, found crawling and wriggling on the gravel.

They are called Detritus because they are detrivores, meaning they feed on rotting plants and fish. They also feed on uneaten food and fish excrements. They are usually found in the substrate or in the water columns.


2. Substrate Detritus

They could be of different colors, like white, red-brown or gray. Identifying that tiny white worm in your aquarium will be quite easy if you pay careful attention to it.

If they have overpopulated, you will see them squirming and twisting around on the substrate. At times you will find them half-embedded inside the substrate, with the other half of the body protruding out, resembling fragile plant shoots sprouting from the ground. This happens when there is a low 02 level in the tank.


3. WaterColumn Detritus

At times you will find another type of Detritus worms squiggling around in the water of the fish tank. They resemble threads twisting and fussing.

You might also find them stuck on the glass near the water surface. They may also gather around the filter, so if you stop-and-restart your filter after changing water, you might be able to see them exploding out from near the filter.


4. Planaria Or Flatworms

This type belongs to the flatworm order of Tricladida, class Turbellaria. They are flat and ribbon-like, with a slightly-pointed head, in contrast to the tube-like bodies of earthworms.

Unlike the peristaltic movement of an earthworm, a planarium slides smoothly, more like a snail, on the glass of the aquarium. These worms in the aquarium exist in various colors— whitish, brown, beige, reddish or spotted.

They love to eat uneaten food of fish and also the flesh of fish. They also love to munch on shrimp, fish eggs and shrimplets. They are nefarious in the sense that they sit on a large fish, and while they take a free ride, they also bite out chunks of flesh from its body.

If left unchecked, they will populate quickly and all you will be left to do is despair. They breed both sexually and asexually. When you cut them into pieces, each piece bears the ability to grow into a new worm. So next time you see tiny black worms in fish tank, beware!


5. Parasitic Anchor Worms (Nematodes)

Although they are called worms, but they are not worms at all. They are crustaceans, like crabs and shrimps. They are given the given the name of a worm because they are dangerously parasitic.

They have a thread-like appearance, almost resembling the shape of the uppercase letter “Y”. They undergo various stages of development, and their free-swimming stage, the male and the female mate.

When the mating process is complete, the female Camallanus burrows into the flesh of your aquarium fish and metamorphoses into the Y-like, wormy, repulsive structure. The way they stick out of a fish’s body would remind you of someone who accidentally brushed into a thorn bush.

Once they have burrowed into the fish’s body, they secrete an acid that corrodes and melts the tissue so that the anchor worm can guzzle it up. They lay eggs which are almost invisible to the eye. Even the babies that hatch from the free-floating eggs cannot be located.


6. Camallanus Gut Worm

They are parasitic roundworm type belonging to the family Camallanidae. They are internal parasites, often infesting the guts of fish like Yellowhead Catfish or Korean Bullhead.

They may infect all fish in an aquarium actually, especially loaches, guppies, mollies and cichlid fish. Female Camallanus lay a large number of eggs which hatch into hundreds and thousands of larvae inside the intestines of the infected fish.

When the infected fish defecates, the larvae come out of the anus and spread in the fish tank eventually turning into meals of crustaceans, like snails. This snail is then eaten by another fish, and the cycle of infestation continues. If the fish are left untreated, they will eventually die.

They are reddish brown in color. Fully developed Camallanus are around 2-3 mm long and look red because they feed on blood. The ways you can tell your fish are infected by them are when the worms protrude out of the tail-region, when the fish start bloating and have lost their appetite.


7. Flukes Or Trematodes

Flukes are flatworms which attach to bigger fish and chew away on their gills, skin and fins, causing inflammation on the fish’s body. If left unchecked, the fish will eventually die.

They are very commonly occurring so every fish keeper can expect at least one fluke-attack. Flukes are microscopic, so the only way to locate their infestation is by observing the fish.


8. Bristleworms, Leeches And Fireworms

Bristleworms are not harmful to fish, they are harmful to you, the caretaker. Yes, they sting really bad if you accidentally touch them. Their stings contain neurotoxins which may cause irritation and inflammation. Fireworms hurt both fish and humans.

Leeches attach themselves to the bodies or the inside of the fish’s mouth and release blood thinners that affect the health of the fish significantly. Common ones are Snail leeches and Asian leeches.


So How Do You Remove These Worms In Fish Tank?


1. Clean The Fish Tank Every Week

Vacuum and siphon the gravel regularly, make sure you check underneath large rocks, inside cracks and every other nook and cranny for uneaten food, fish excrements and rotting carcasses, all of which are food to worms in fish tank.

Vacuum carpeted plants and leaf surfaces also. Remember to clean the filter regularly.


2. Change Water

Change 10-20% water every week, whether or not you have a worm infestation. In order to know how dirty you fish tank is, create a disturbance in the water body with a cup or a sieve, or simply with your hands (better if you wear gloves!), and take note on how much debris floated up.

If you see too much of it, go for a 30-50% water change every week. Changing water is the inevitable ultimate way to remove parasites in your aquarium.


3. Avoid Overfeeding

Each time you feed, make sure the food quantity is so that it gets eaten up within 5 minutes. Feeding fish 2-3 times a day is sufficient. Remember fish have a tiny stomach, and cannot assimilate excess food.

They may appear to eat a lot but most of it do not get used up by their body, instead passes out as waste. So overfeeding is absolutely unnecessary. If you feed excessively, the extra uneaten food will serve as a buffet for the Detritus worms to feast on.

In a very short period of time, a handful of worms will grow into a few hundred, infesting your whole tank.


4. Do Not Overpopulate Your Tank

If you are new at fish keeping, add only 3 fish at a time in your new tank. Cycle your tank first. Add a few live plants, and sprinkle some fish food to start the cycle. Once you see that the plants have started growing, you would need to understand that the nitrogen cycle is complete.

The most common rule to calculate how many fish you should keep in your tank is the “1 inch per gallon” rule. The rule dictates that for every gallon of water, you can keep one inch of fish.

However the rule varies depending on the shape and age of your fish. If your tank allows you to keep 20 fish in it, place 15; that would be a wise decision for you in the long run.


5. Setting Of Traps

You can make a worm trap right at home. Take a translucent or opaque plastic bottle, and make 4/5 holes on either side of the bottle, to fit plastic tubes through. The plastic tubes should be long enough to be inserted into the substrate of the fish tank.

The idea is that the worms living in the substrate would smell the bait inside the bottle, enter through the tubes, and get trapped in the bottle. The bait could be fish food or fish flesh.


6. Introduce WormEating Fish

Tiger Dwarf Loaches and Red Dot Gobies like to feed on planaria worms.


7. Quarantine

Separate the worm-infested fish and house it in a new 20-30 gallon tank. Set up this aquarium in the same way as you would with any other fish tank. Do not use porous rocks or gravel as they will absorb medications and make space for worms to populate again.

Carbon and mechanical filter-media should be removed as they might absorb medications. An aerator or aeration pump could be introduced. All nets, siphons, sieves and scrapers used for this quarantine tank should never be used for the old tank, and vice versa. Keep disinfecting the tools after each use.


8. Chemical Methods to remove bad worms from the fish tank

They are effective at removal of freshwater worms of all sorts.



They are very small, only about 0.1 to 0.6 inches, and almost unsightly when they are less in number. They become visible only when they have overpopulated and infested the whole tank.

They should better be removed at once since they are carnivores and do not hesitate even once feeding on your fish. Every aquarium keeper wants to know how to identify and kill planaria in easy way.

You can try some dog deworming products like Panacur C, which contains the active ingredient fenbendazole that is effective against planaria worms. For every 10 gallons of water, add 0.1gm of the product.

Remember though that fenbendazole may prove to be harmful for snails and some fish, so before treatment, move them to another tank.

There is another product named Genchem No Planaria that contains betel nut extract known to be effective against gut parasites. Dead worms, after treatment, could be removed easily by weekly water changes of 10 to 50%.

Other products such as API Clout Parasite Treatment, containing a neurotoxin, is quite effective at depopulating plenaria.


Anchor Worms And Fish Lice

Dimilin X is a product which is great at removing anchor worms and fish lice. One drop is enough for 5 gallons of water.

Anchor worms stick like thorns from your fish’s body, so you might prefer to use tweezers to pull them out, but it might be a bad idea. When you pull out the anchor worm, some flesh might also rip off, causing secondary bacterial infections in your fish.

You can also use methylene blue or hydrogen peroxide to treat fish wounds to reduce the possibilities of infections. Remember that there might be a lot of invisible eggs and babies of anchor worms floating around in the water, so Dimilin X and regular water change will help a lot.



Products containing levamisole hydrochloride, fenbendazole or praziquantel will help. These ingredients, however, do not kill the worms but paralyze them. After treatment, leave the tank undisturbed for 24 hours.

When you check on the tank later, you will see reddish poop-like things coming out from your fish’s rear which would be the paralyzed worms slowly detaching themselves from the fish’s gut.

You are bound to find motionless worms floating around or lying on the substrate, then is the time to change 70-100% of the water, followed by gravel vacuuming. This treatment should be repeated every 3 weeks for 6-9 weeks.

Remember whichever treatment you opt for, consult with an experienced fish vet before you proceed since such anti-parasitic drugs could prove to be harmful for fish life. Before the treatment, remove snails and shrimps to another tank.

Avoid CuSO4 treatments and antibacterial products since they do more harm than good.



Potassium permanganate bath is effective against fluke infestation. Add in this proportion—10ml/l and let your fish stay in that bath for 20 min.



leeches could be removed by bathing the infected fish in salt solution for 20 minutes. Physical ways of removing leeches by using tweezers might cause infections in the fish’s body.



The best way to remove them is to cut off food supply. Therefore, feed less, carry out nitrogen cycles, and change water.




1) How did the worms end up in my tank?

Ans: When you shift materials and organisms from an old tank to a new one, or from a store tank to your home tank, eggs or larvae of these worms may hitch-hike their way to your tank.

Gravel, plants, decorative items and even filters may be infested with worm eggs and larvae, and you will not even notice since they are unsightly.

Overfeeding and improper tank maintenance are other top reasons for worm infestations. Less oxygen and low pH could be other reasons. Also avoid using tap water or pond water for filling up your tank.


2) Are all worms in fish tank dangerous?

Ans: No. Detritus worms, those tiny white bugs on aquarium glass, for example, feed on uneaten fish food and fish excrements, and they lie around peacefully in the substrate, so they are quite beneficial. Problems start when they overpopulate.


3) How will I locate the invisible worms?

Ans: Look for signs and symptoms of illness in your fish, since the worms may be unsightly. Worms are often nocturnal, meaning they come out at night or when the interior of the tank is dim or dark.

So there is a higher possibility of you being able to spot some of these bad guys when it gets dark. You can also use red light to see them better.


4) What are the symptoms of infection in fish?

Ans: Fish’s eyes go cloudy or red, and red, white or golden spots appear on the fish’s body, or fins might be clamped.

Look for abnormal behavior in fish. Infected fish will act lethargic, won’t eat, will hide behind rocks, swim recklessly or rub their body against glass or rocks. They might breathe faster, look bloated, eat a lot but not gain weight.

Finally look for anything reddish and thread-like coming out from their rear which is a sure sign of infestation.


5) What precautions should I take to minimize the chances of worm infestation?

Ans: Keep your tank clean, do not overfeed, change water regularly and do not overpopulate the fish tank. Also do not shift decoration items, gravel, filter and such items from an old tank to a new one without first disinfecting or sterilizing them.

Also refrain from using pond or tap water in your aquariums. Use natural plants instead of artificial ones, for nitrogen cycling.


6) Are aquarium worms harmful for humans?

Ans: Depends on the type, category and subcategory of the worm in question. Stay on the safe side though, by using precautionary measures before disinfecting the tank.

You may wear gloves or hire an aquarium keeper to do the work for you. Wash your hands thoroughly after handling anything out of an infected tank. Do not discard the water of an infected fish tank via the kitchen or bathroom sink.


Final Word

Worm in tanks could cause your fish to lose appetite, act abnormally, bloat, suffocate and even die. If you love your aquarium friends, you would definitely not want them to suffer like this.

Worms in fish tank, types and how to get rid of them are all connected to each other. When you buy a new fish, quarantine it to ensure it is disease free. When you buy decoration items, gravel and filters, ensure they are sterilized before placing them in your new tank.

Most importantly, keep your tank clean and change the water regularly. If worm infestation is massive, go for chemical treatments.

Keep a close eye on your aquatic friends and look for signs and symptoms of the disease. Do not neglect them because you are responsible for them.


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