3 Tiny White Worm Types in The Aquarium Fish Tank

Having a fish tank at home entails a healthy and safe environment for your pets. Over time, you will likely introduce or add new pets to your tank. Although adding new animals may seem fun, it poses a threat of introducing worms, parasites, or bacteria into the tank.

Measures are available to mitigate and avoid the spread of this issue. You are reading the right article should you find yourself with a tiny white worm issue.

You will find these creatures floating or crawling in a freshwater aquarium. Some are harmless, while others can pose a threat to your pets. Regardless, knowing how to prevent the spread and worsening of the infestation is helpful. 


The three most common types of tiny white worms in the fish aquarium’s tank are Detritus Worms, Rhabdocoela Flatworms, and Planaria Flatworms.

Types of tiny white worms in the fish tank

fish tank

The three tiny white aquarium worm types in a fish tank are the Detritus, Rhabdocoela, and Planaria worms. Freshwater work identification is important before determining the action items. We proceed with other necessary steps as soon as we identify the type.

Identifying these is important because not all white worms are harmful. We recommend using a magnifying glass to find the type because the differences are minor. 

The most common way of introducing these creatures into your aquarium is through new aquatic decor, pets, or plants. 

1. Detritus Worms (roundworms)

The Detritus is the collective term we use to identify roundworms in freshwater systems, such as an aquarium. These are part of the ecosystem, which you will usually find in the deeper parts of the tank. They help break down unconsumed food and waste.

These worms will come out of the substrate whenever oxygen levels are low. You will find them floating through the water or on the tank glass. Thus, it is unlikely these creatures can pose a threat to shrimps or fish.

You will find this more in shrimp tanks because carnivorous fish eat them. Thus, they stay away from these fishes. You do not have to do anything if you find these worms in your tank.

Scientific name:Naididae
Higher classification:Haplotaxids
Family:Naididae; Ehrenberg, 1828

Identifying Detritus

Below are some significant points worth considering when identifying the Detritus worm.

  • Thin bodies resembling white hair or thread.
  • They stay small and will not grow more than 1.27 cm / 0.5 inch.
  • The Detritus is wiggly and active, unlike flatworms.
  • They float in the water instead of gliding.
90 Gallon Aquarium

How to get rid of them

Though they are harmless and will unlikely cause danger to your pets or humans, how can you get rid of them? Some pet owners don’t like them because they look unpleasant.

An outbreak of white nematodes is something you that requires close attention. Staying on top of maintenance work should be a priority at this point. Scheduling regular maintenance and cleaning should mitigate the issue. It will gradually reduce their population until it reaches a normal level.

Here are some things worth considering when getting rid of them.

  • Vacuum the substrate area more often.
  • Use an airstone to oxygenate the water.
  • Reduce the food amount you feed your pets.

The Detritus will visually disappear as soon as the nutrient levels in your tank are back to normal levels. It is likely a small group of them will remain in the substrate. Frequently using a gravel vacuum will aerate the substrate. As an effect, the Detritus will stay underneath it.

Attaching an air pump to an airstone helps keep oxygen levels in the fish tank within normal levels. High oxygen levels will keep the Detritus from sticking out of their heads. On the other hand, events that lower oxygen levels in an aquarium cause them to surface.

The following are events that may lead it to happen:

  • A malfunction in the HOB filter. The water movement from the HOB filters oxygenates your tank.
  • Heterotrophic bacteria grow during cycling. The water will look foggy.
  • Temperature increase in the water decreases oxygen. Cold water holds more oxygen than warm water.
  • The growth of phytoplankton. These use a lot of oxygen at night.
  • An overdose of water conditioners can deplete oxygen levels in the tank.
  • Overcrowding in the aquarium.

On the other hand, an abrupt change in the aquarium’s parameters will also cause nematodes to surface. 

2. Rhabdocoela Flatworms

The aquarium Rhabdocoela worms feed on microalgae and bacteria. They are harmless and will not attack your pet shrimp or fish. The Rhabdocoela is part of your tank’s ecosystem and will coexist with other organisms. You will also find them circling the body of dead fishes or plants. The Rhabdocoela is among the most common white flatworms in aquariums. 

Scientific name:Rhabdocoela
Higher classification:Rhabditophora
Order:Rhabdocoela; Ehrenberg, 1831

Identifying Rhabdocoela

Below are some significant points worth considering when identifying the Rhabdocoela flatworm.

  • They are tiny, measuring only up to 0.2 inch / 0.5 cm.
  • These worms glide along the aquarium glass (do not wiggle).
  • The Rhabdocoela has two round ends.
  • They do not have a triangle-like head.

How to get rid?

The Rhabdocoela grows in number because of excessive nutrients in the water tank. Vacuuming the tank gravel more frequently will get things in control. 

Another thing you can do is to minimize the food you offer. Moreover, carnivore fishes may also eat the Rhabdocoela worms. A good example would be the Betta fish, which loves feeding on worms and small crustaceans, including the Rhabdocoela.

3. Planaria Flatworms

The Planaria flatworm is a species of carnivorous flatworm. By nature, they are predatory, causing harm to your fish or shrimp. Among the three types we have covered, this is the one you do not want swimming in your aquarium. 

Aside from fishes and shrimps, the Planaria can harm freshwater snails too. At night, they feed on baby shrimps and their eggs. 

Molting adult shrimps can also be at risk from an attack from the Planaria. Some aquarists observed the Planaria paralyzes live adult shrimps before attacking, which is an implication of using toxins. To date, no research relates the Planaria with toxins, but it is also worth mentioning this species is not well-researched. 

Some peer-review studies suggest that land-based Planaria flatworms produce Tetrodotoxin, a neurotoxin type. Tetrodotoxin is the same neurotoxin you will find in marine pufferfish. The best action is to remove these worms as soon as possible.

Scientific name:Tricladida
Higher classification:N/A
Order:Tricladida; Lang, 1884

Identifying Planaria

The following are some points worth considering when identifying a Planaria flatworm.

  • A young Planaria has a distinctive triangular head with two eyespots.
  • The adult Planaria can grow up to 3.8 cm/1.5 inches. Their body length will remain around 2.54 cm/1 inch.
  • The adult Planaria may develop a pink tint on their body.
  • They are slow movers and prefer creeping on surfaces. These worms do not wiggle or float.

Several times, people misidentify the Planaria as a Rhadocoela or vice versa. They are easy to tell apart. The Rhabdocoela has rounded body ends and is relatively small. On the other hand, the Planaria has a spade-like head and grows large. You will likely encounter a Rhadocoela than a Planaria in your tank. 

How to get rid?

The Planaria are dangerous creatures, so eliminating them should be a top priority. Do take note they are not much of an issue in tanks that dominantly contain predatory fishes. As long as it fits in the mouth of the fish, the worms are in bad luck!

However, you always cannot add a predatory fish to your tank. It does not make sense to add a predatory fish if you have a shrimp tank to counter the Planaria. The predator will hunt down and consume all the shrimps faster than the Planaria.

You are down with two options in this case:

  • Use a worm trap to export the Planaria off the tank.
  • Use chemicals to kill them.

Worm Trap

A DIY worm trap is a container:

  1. Place some food inside the container.
  2. The worms will enter to consume the food.
  3. Remove the container with the flatworms inside.
  4. Repeat the process until they are all gone. 

There are several traps available online, which you can purchase easily. However, you can also make your own by following these simple steps.

  1. Look for a 16.9-ounce plastic bottle or something similar.
  2. Thoroughly rinse the bottle.
  3. Make four holes in the bottle’s bottom using a pin or needle.
  4. Place a small number of fish flakes inside.
  5. Attach the cap and tighten it.

It is worth noting not to put too much fish food inside the trap. It can cause Nitrite and Ammonia levels to rise, which is more devastating to shrimps than Planaria.

The holes in the trap should be small to prevent ineffectiveness. The Planaria can squeeze their body in tight spaces, so they will eventually get inside. 

Dewormer (Chemical)

A chemical dewormer is an effective way of eliminating Planaria. Several aquarists recommend Panacur C, which is an effective canine dewormer.

Remove the carbon filter media before beginning the treatment. We recommend following the instructions..

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