Many aquarists are frightened when they see small white worms in their aquariums. Indeed, it is not a pleasant sight, but there is no need to panic. Most often, these are so-called free-living nematodes — common inhabitants of a healthy aquarium that feed on food residues and decaying organic matter. They are not dangerous to fish.
However, their sudden and massive appearance is a signal for you. It indicates that too much waste has accumulated in the water. Perhaps you are overfeeding your fish or rarely cleaning the substrate. The worms themselves are not the root of the problem, but only its manifestation.
You don't need chemicals to get rid of nematodes. It is enough to clean up the aquarium. Thoroughly clean the substrate with a siphon, reduce food portions, and remove excess organic matter. Many fish, such as young gouramis or swordtails, will happily eat excess worms. After a while, the balance will be restored, and there will be very few visible worms.
What are nematodes?
There are up to 24,000 species of nematodes in nature. These are long worms with a round cross-section and a smooth body. Their length ranges from 80 micrometers to 8.4 meters. Females are usually larger and may be barrel-shaped or lemon-shaped. The head shows signs of three-ray symmetry.
Nematodes are predominantly dioecious, but hermaphrodites are also found. The worms lay eggs to reproduce. However, scientists have also discovered viviparous species of these fauna representatives.
Types of nematodes
Nematodes can be free-living or parasitic. The former do not harm aquatic life. The latter are very dangerous and can cause fish to die.
Free-living nematodes are an important component of their ecosystem. They live in soil, saltwater, and freshwater bodies. Many species settle at the bottom and process organic matter. Free-living nematodes are difficult to miss in an aquarium, as they are constantly moving and resemble thin snakes, whose population grows quite rapidly.
A number of nematode species have become parasites or commensals of animals. These worms cause invasive diseases in plants, animals, fish, and even humans.
Parasitic species infect fish through waste products or directly. Nematodes most often affect tropical species of aquarium vertebrates.
One worm-infected fish can infect an entire colony in a matter of months.
Why do nematodes attack aquariums?
The following can be sources of nematode infection in aquariums:
live food;- infected plants, sand, stones;
- snails;
- the fish themselves.
One of the reasons roundworms begin to multiply rapidly is overfeeding of fish. Uneaten food residues settle at the bottom and become an excellent breeding ground for nematodes.
What is the danger of nematodes?
Free-living nematodes in an aquarium do not pose a danger to its inhabitants. Some species of fish, especially young fish, eagerly eat small worms resembling tiny earthworms or fungal mycelium, as the parasites contain the entire spectrum of nutrients they need.
The situation is worse with parasitic species. These worms infect both farmed and wild fish. A high load leads to disease and death of the host.
There are more than 600 known species of roundworms that are dangerous to fish. The most common are:
- Capillaria — settles in the intestines of cichlids, cyprinids, gouramis, and tetras. Female worms are easily recognizable by their brown, barrel-shaped eggs with a “plug.”
- Eustrongylides — they affect the host's muscles and are dangerous for guppies, danios, and angelfish. Infected fish develop a swollen abdomen, as the worms often migrate to the abdominal cavity. Eustrongylides worms are red in color, very long, and twisted into a ring.
- Camallanus — a species dangerous to cichlids and livebearing cyprinids (guppies and swordtails). Fish infected with Camallanus are easily recognizable by the red worm protruding from the anal opening. The parasite lives in the intestines.
- Contracaecum — parasite larvae develop in fish. Tilapia, centrarchidae, caproidae, and perch are usually affected. The parasite is found in the liver, heart, and swim bladder, and does not always cause disease.
Adult parasites are found in the digestive organs of fish, and some species settle in other parts of the body, including deep layers of skin, fins, etc.
With a minor infection, the herd may not show any symptoms of the disease. However, the reproductive capacity of such individuals is reduced. Young fish infected with the parasite do not develop well.
In case of infection, it is necessary to identify the carrier fish. At the initial stage, the individual does not differ from its relatives, but it is larger than usual. Gradually, lethargy appears, the abdomen becomes rounded and swollen.
Fish infected with nematodes
If there are a large number of worms in the fish's body, its spine becomes deformed, leading to the death of the infected individual.
The following also indicate nematode infection:
- hemorrhages;
- lumps on the body;
- foci of inflammation;
- tissue necrosis;
- cysts (bubbles), granulomas (nodules).
Diagnosis
An accurate diagnosis is made by examining the body of the dead fish. Another method of diagnosis is a biopsy of the damaged external tissues. It is also possible to examine the fish's feces for parasite eggs. The feces must be fresh, as after a few hours the biomaterial is colonized by non-parasitic nematode species. The second method of diagnosis is most often used for valuable fish species.
How to combat them?
- If nematodes have infested the aquarium, increase water filtration and soil siphoning, and reduce the amount of food for fish and snails.
- It is quite easy to combat free-living nematodes. Mollies and gouramis eat certain types of worms: they can destroy a worm population in just 2–3 days. Snails also eagerly feast on these uninvited guests.
- Worms are sensitive to temperature increases. Therefore, slightly heating the water by 2 °C helps to get rid of the inhabitants. If the worms do not die, then they are not nematodes, but other types of parasites.
- Another simple way to get rid of small worms is to catch them with a small net.
There are also more radical methods of control. Experienced aquarists share that the nematode population can be destroyed by heating the water to 40–45 °C. Before the procedure, fish and plants are removed from the aquarium. Decorations are removed, washed, and disinfected. After the water has cooled to the required temperature, the plants and fish are returned to the tank. Heating the water even gets rid of individuals that have burrowed into the ground or hidden behind stones.
Scientists have found that what is bad for fish is good for parasites. The worse the conditions in the aquarium, the more actively the worms reproduce. They are able to survive even in the complete absence of oxygen. But without moisture, they die. The most difficult parasites to combat are nematodes.
Fish treatment
Before treatment, the aquarium is cleaned of organic debris and feces. This will prevent secondary infection. Sick fish are placed in quarantine.
Two drugs are used to treat fish for roundworms:
Levamisole
The drug is used as a feed additive and for bathing. The dosage is 4 g per 1 kg of feed once a week for 3 weeks. For bathing, the drug is diluted to 2 mg/l and treated for 24 hours. The treatment is repeated after 2–3 weeks.
Fenbendazole
The product is used only as a feed additive. The dosage is 2.53 g per 1 kg of feed every 3 days. Repeat treatment is carried out after 14–21 days.
Other antihelminthic drugs are also used against worms:
Tetra Medica CestoNemaEx
(diflubenzuron) Dosage: 20 ml per 400 l of water.
Sera Med Professional Nematol
Dosage: 10 ml per 400 l of water.
JBL Nemol
(benzimidazole) Dosage — 100 ml per 400 l of water.
These products have a broad spectrum of activity and can be used to combat other worms.
The most difficult to treat are fish whose gastrointestinal tract is not infected, but other organs are. Often, the only way to treat extraintestinal forms of worm infestation is through surgery. Therefore, infected fish are usually discarded.
Nematodes in an aquarium are small worms that often scare beginners, but in fact, they are rarely dangerous to fish. Most often, they appear due to excess food or poor cleaning of the bottom and live in the soil, feeding on food debris and organic matter. Their presence alone does not usually harm the inhabitants of the aquarium, but a large number of them is a sign that it is time to clean up: feed less often, change the water more often, and clean the substrate. Getting rid of them is easy—just improve your care routine, and if they multiply rapidly, you can temporarily introduce fish that eat them, such as some catfish or guppies. The main thing is not to panic and not to pour chemicals thoughtlessly, because the problem is most often solved by simple cleaning.
Prevention
A few simple measures will eliminate the need to deal with worms.
Every 7 days, the aquarium must be cleaned and the water partially changed. Before using stones and decorations, they must be thoroughly disinfected. Stones are cleaned of moss and dirt and calcined in the oven.
The decor is also washed with warm water and, if the material allows, left in a pink solution of potassium permanganate for a day, after which it is rinsed and allowed to dry. Soil and sand can also be kept in the oven.
If you cannot do without live food, it is better to buy it in stores rather than catch it yourself. You need to be especially careful when feeding fish with tubifex, insect larvae, and copepods.
FAQ
Are free-living nematodes dangerous to humans?
Worms living in an aquarium are not harmful to humans. This species of nematode is adapted to living only within the aquarium ecosystem.
Is it possible to become infected with parasitic nematodes?
You can become infected by eating contaminated raw fish or by ignoring hygiene rules.
Can purchased fish be placed in the aquarium immediately if they show no signs of worm infestation?
No, this should not be done, even if the individual appears healthy. First, it is placed in quarantine, and only after ensuring that it will not harm other inhabitants is it moved to a permanent location.
So, should you be afraid of nematodes in your aquarium? In most cases, no. These worms are a natural part of the aquarium ecosystem and are usually harmless. They even do useful work by processing waste. There is no need to panic when you see them.
The main thing is control. If there are too many worms, this is a sign of overfeeding or excess organic matter. Start by cleaning up: siphon the soil, change the water, and reduce the amount of food. Often, these simple measures are enough to bring the population back to normal.
Only use special medications as a last resort, if you are sure that these are dangerous parasites and the problem is really serious. For most free-living nematodes, this is unnecessary and can harm the balance in the aquarium.
Remember that a healthy, well-maintained aquarium with clean water and proper feeding is the best protection against any unwanted outbreaks. Focus on maintaining balance, and your fish will live peacefully alongside these tiny neighbors.
