The purpose of this article is to provide a simple explanation that includes cause, remedies, misidentification, and possible dangers or other indicators of these commonly observed "wiggly worms" in aquariums.

The owner of Fish beginner has a stake in this particular article as he mistakenly read many of the incorrect articles and social media forum posts about Planaria and Detritus Worms and dumped in strong de-wormers which are OK with the small numbers of Planaria that are present, but is deadly to the entire taken when used to eradicate the much more common decomposting Detritus Worms.

This article is written in a simple question and answer FAQ format to hopefully help readers past the circular incorrect information that is unfortunately growing..

Some of this information is courtesy of:

"Aquarium, Pond Fish Parasites; Trematodes, Flatworms, Nematodes, Detritus, Anchor Worms"

AND

"Aquarium Planaria, Detritus Worms; What is correct"

Please see the above articles for more.

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The picture to the left provide a close up view of what these look like, with the picture further to the left magnified even more. Please click to enlarge further.

However to the naked eye these are only about 1/8 inch or 3 mm, although many professionals have seen these longer (up to 3 cm). When the population explodes and/or oxygen levels are low, these thin as a hair and white worms can even be seen swimming though the water in the middle of the aquarium.

What these are NOT are Planaria, which these are commonly and inaccurately misidentified as.

This article I noted earlier deals with this unfortunately common misidentification:

"Aquarium Planaria, Detritus Worms; What is correct"

How these worms get from one aquarium to another is not 100% clear, most likely from plants (especially rooted plants), substrate transfers and simply aquarium water when fish are purchased (as small microscopic worms).

What is clear is these worms usually go unnoticed until something causes a population explosion, then these worms can be observed swimming vertical near the surface of the water or crawling on the inside glass of an aquarium.

First, prior to population explosions, these Detritus Worms are living "quietly" in your aquarium substrate/gravel or even bio filters, when the amount of dissolved oxygen in the aquarium water falls to levels where by there is not enough oxygen under the substrate and the worms seek oxygen near the water's surface.

More commonly, the population increases to saturation points from over feeding and/or poor aquarium cleaning practices that simply feed these worms. As well this in turn can decrease oxygen levels from simply too many worms that then force the worms out of their hiding places. 

Yes, besides living in your aquariums substrate and detritus within the substrate, these annelid worms can also popular your filter, most commonly the bio filter areas of your filter. A common example would be the ceramic filter media of a canister filter.

This is where correct identification is important, as a Detritus Worm is generally not dangerous in the normal numbers usually found in an aquarium.

In fact, in normal usually unseen numbers, Detritus Worms are actually beneficial helping to compost organic wastes in an aquarium similar to their cousins the Earthworm in a compost heap (both worms are annelids too).

Any danger stems from an over population that then lowers oxygen levels, which in turn affects fish health.

As well an over population is often an indication of poor aquarium husbandry which can lead to other issues down the road such as an Aeromonas infection

First let me point out that Planaria are carnivores or aggressive scavengers that in particular can be dangerous to fish fry or eggs and these generally should be eradicated, even by chemical means if needed.

However with much more common Detritus Worms, since these are generally found in VASTLY greater numbers in an aquarium than Planaria are ever found in (generally 1000s to every 1), the use of chemicals on the Detritus Worms can cause such massive die offs that an entire aquarium of fish can be killed off just from the poisons emitted from the dying Detritus Worms.

Unfortunately I know of many who have lost many of their fish by just such misidentifications that have been put forth by many websites and aquarium forums.

For true Detitus Worms, which 85-90% of persons who have initially identified as Planaria turn out to be, the remedy does not include any medications or snake oil treatments someone may be attempting to sell you.

The remedy is a good cleaning of your aquarium substrate (Gravel/Sand) preferably with a gravel vacuum while changing the water.

In between water changes the use of a Sludge/Detritus Remover Vacuum can be very helpful too.

With both you likely will remove many unwanted over population worms in the process of removing much of their food source.

As well, often improving the food source with a more highly digestible diet such as the Ultra Premium "Clay Neighbor's Custom" of fish foods will lower the wastes that these worms feed on.

Product Resources:

"Clay Neighbor's Custom" Where it is about the analysis, not just the ingredients (the only premium fish food that goes beyond quality ingredients to quality science/experience based analysis!)

Aquarium Detritus Remover Vacuum & Standard Siphon Gravel Vacuums

Improving filter media can sometimes help as well, using products such as AAP Matrix or Volcanic Aquarium Rock can help since these are very porous and allow better aerobic nitrification and thus breakdown of organic waste.

As well these two filter media allow for de-nitrification which then lowers nitrate levels in the aquarium as well and in the end lowering mulm and over all organic waste that these composting worms feed on.

Both of these products are easily used in canister filters, and some HOB filters such as Aqua Clears with the AAP volcanic rock being a very inexpensive product.

Further Reading:

Aquarium Filtration; About

Aquarium & Pond Filter Media, Material; Mechanical, Bio, Chemical

Make sure you rinse your aquarium filter media, such as sponge, bio rings, etc. This should be done with de-chlorinated tap water or used aquarium water you intend to throw away.

Consider adding another Aquarium Air Pump or another bio filter, of which a Sponge Filter is difficult to beat for simplicity and efficiency (but for maybe the Fluidized Sand Bed Filters).

Reference this article for more about the use of sponge filtration/filters; Sponge Filtration; Sponge Filter Information

Please reference this article for more about aquarium cleaning:

Aquarium Cleaning; Reasons, Methods, more

In summary, since occasionally lack of aquarium filtration, lack of cleaning of filter media, and lack of good water circulation and aeration are issues, CORRECTING these can be quite helpful to the control of these Detritus Worms which are not necessarily a "bad" thing to have in your aquarium, but a population explosion is often an indicator of issues with ones aquarium and can decrease dissolved oxygen available for fish.

Product Resources:

AAP Matrix Filter Media

Premium Volcanic Rock

Million Air, SunSun Aquarium Airpumps

Premium Hydro Sponge Aquarium Filters from 'American Aquarium'

TMC Premier FSB Aquarium Filter

Now if these are truly Planaria; chemical treatment is often called for. What is worthy of note is that Planaria are tough and generally the mild & snakeoil treatments often recommended that may work for Detritus worms, will not work for Planaria.

Our opinion here at Fish Beginner is that since Internet articles, social media, etc. has so confused the facts about Planaria and Detritus Worms, that much of what supposedly works for Planaria was actually used for Detritus Worms. It is also worthy of note that generally treatments effective for Planaria are NOT shrimp or snail safe.

So with this in mind, Fish Beginner recommend the stronger treatments that true aquarium keeping professionals recommend [such as Carl Strohmeyer].

Here are our recommendations:

- Dyacide or any product containing Trichlorfon (Dylox). This is one of the most sure treatments for Planaria, but make sure snails, shrimp are removed

Recommended Product Sources:

AAP Dyacide

AAP Clout (also contains Trichlorfon)

- AAP/API General Cure or Tetra Parasite Clear. Not nearly as strong, but safer, especially for silver fish

Recommended Product Source: AAP General Cure

- Levamisol

- Copper Sulfate such as found in Cupramine can work if at levels of .25 ppm, but not higher than .30 ppm or lower than .20 ppm