Nematodes (White Worms) In The Aquarium | Prevention

Last updated on December 24th, 2022 at 11:05 am

Novice hobbyists panic when nematodes (white worms) appear in the aquarium. These are nematodes that can multiply rapidly in a favorable humid environment. The worms look ugly in the aquarium water, make them frown with disgust, but getting rid of them is easy. 


It is believing that worms begin to actively reproduce when the owner does not take care of the reservoir, in fact, they can appear even with the correct content of the fish.

Types Of Aquarium Worms

Worms in an aquarium are common. Some species are harmless, others are parasitic and pose a danger to the inhabitants of the reservoir. When looking at the aquarium water from a distance, it seems that all the worms look the same. There are actually the following types of worms:

  • Planaria are ground worms. They are selecting outside when changing water parameters: temperature, pH, hardness. These are parasites, reaching a length of 2 cm. They are dangerous not only for fish but also for aquarium crustaceans.
  • Turbellaria is a parasite that is dangerous for eggs and fry. These flatworms live in the aquarium mainly on the glass. Having multiplied strongly, they harm the aesthetics of the aquarium ecosystem.
  • Hydra is a worm, harmless to adult fish, occasionally affecting eggs and fry. Torn in half, does not die, but regenerates into two individuals.
  • Nematodes in an aquarium are harmless inhabitants. In length, they reach 2 mm. Some aquarists breed them specifically for feeding fish.
Types Of Aquarium Worms

Reasons For The Appearance Of Nematodes

Nematodes are one of the most common microscopic worms on the planet. They live in colonies, move actively and almost continuously. They are unusually hardy, and when environmental conditions deteriorate, they do not inhibit vital activity but begin to multiply intensively. Due to the anaerobic type of respiration, they live even in an oxygen-free environment. They only need moisture: they die in dry conditions.

White worms are not hermaphrodites. Females are much larger than males. They reproduce by laying eggs. These worms live in an aquarium on glass, settle on stones, in the ground, but prefer free movement in the water column. It is not uncommon for white worms to form a colony near the filter in an aquarium, as the currents created by the device help them move.

Reproduction of nematodes in an aquarium is almost inevitable. There are two main reasons for uninvited occupants:

  1. Overfeeding fish. When the fish does not eat the food completely, it sinks to the bottom, decomposes, becoming a favorable breeding ground for helminths.
  2. Purchase of contaminated animals and decor items for the aquarium. Nematodes and their eggs can found on plants, fish, molluscs, in the substrate. In this case, the correct feeding of the fish and the maintenance of the aquarium does not matter.
Types Of Aquarium Worm

Infection Of Fish With Nematodes

There are several thousand species of nematodes on the planet. Some are harmless, others are parasitic, gripping plants and animal organisms. Usually, white worms in an aquarium are non-parasitic nematodes. But the risk of contamination of fish with a parasitic species exists. Infection can be direct (when a sick individual touches a healthy one) or through waste products.

It is impossible to understand early on that an aquarium fish is infected. The behavior of the individual does not change, only appetite increases slightly. As the parasite multiplies, symptoms appear: the fish becomes lethargic, inactive, its belly swells, which causes the spine to bend.

The infected individual dies, but if it not removed, it will infect all the inhabitants of the reservoir before dying.

White Worms

Controlling Nematodes In The Aquarium

If white worms of a non-parasitic species have settled in the aquarium, then there is nothing to worry about. Nematodes are a wonderful live food for fry and adult fish. But many aquarists are still looking for ways to control worms because it becomes unpleasant to look at an aquarium that should perform a decorating function in a room.

Related : Why Is My Fish Tank Cloudy? | Main Causes And Cure

Fighting Worms At Home Is Not Difficult

  1. If the worms in the aquarium in the ground have multiplied due to rotting waste, replace the water, siphon the bottom regularly. The water must change once a week by 20-30% of the volume.
  2. Do not overfeed your fish so that the food does not remain on the bottom.
  3. A good way to treat in a shared aquarium is to add worm-eating fish. Almost all aquarium fish willingly eat nematodes. Settle into a common aquarium molly, Tetraodonov, gourami, Makropody. In a couple of days, the fish will eat all the nematodes. Coils can lodge from mollusks; they also love to feast on worms.
  4. An effective way to get rid of worms is to raise the water temperature by a couple of degrees, add a little salt to the aquarium. For fish, a slight change in parameters is not dangerous, and nematodes are extremely sensitive to such effects.
  5. You can apply a radical method of treatment. Move all inhabitants to a temporary tank. Pull the décor out, rinse thoroughly under hot water. In the aquarium itself, heat the water to 40-45 ° C, leave for 2-3 hours. High-temperature exposure kills even worms hidden in the ground. When the aquarium water has cooled to a comfortable temperature, return the inhabitants to their original reservoir.

If the small white worms in the aquarium turn out to be parasites, then you will have to fight them with the help of chemicals. Suitable medicines for parasitic disease in fish are JBL Nemol, Tetra Medica CestoNemaEx, Sera Med Professional Nematol. How to treat fish, read the instructions on the package. When used correctly, the medicine does not cause side effects, does not inhibit the beneficial aquarium microflora.

Aquarium Worms


To prevent nematode breeding, clean your home tank weekly, change the water. Control the food of the fish, make sure that they eat all the food.

In order to prevent the second reason for the reproduction of nematodes – placing infected animals and decor in the aquarium – buy everything, you need in a specialized store. Disinfect the purchased decor items before placing them in the tank – keep them in water heated to 50 ° C. Buy live food, do not collect near natural reservoirs. In nature, small organisms that fish feed are often infesting with parasitic worms.

Finally, it is worth telling whether parasitic nematodes are dangerous to humans. Aquarists need not worry, cleaning the tank will prevent them from getting infected. Parasites can enter the human body only through the digestive tract. That is, infection is possible if a person eats low-quality sushi or other raw fish dishes. 

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