FAQs on Freshwater Worms of All Sorts, Identification
Invertebrates for Freshwater Aquariums by Neale Monks,
Choose Your Weapon: Freshwater Fish Disease Treatment Options by Neale
Identification 1, FW Worm ID 3,
FW Worm ID 4, FW Worm ID
5, Freshwater Worms 1,
Freshwater Worms 2, Planaria, FW Worm Behavior,
FW Worm Compatibility/Control,
FW Worm Selection,
FW Worm Systems,
Worm Feeding, FW Worm Disease,
FW Worm Reproduction & FAQs
on: Worm Caused Diseases,
Worms as Foods,
FW Invert.s 1,
Wormlike wigglers in cycling tank
Can you guys identify what these are? They appear to be little white
worms in the water but zoomed in they look like larvae of some type.
This is in a new setup about 4 weeks old, no fish, fresh black onyx
sand, RO water, and 81 degree temp. They seem to have come out of no
where. Thanks in advance. Video below image.
<Midge larvae or something similar. Totally harmless, and likely fish
food if you add anything insectivorous of appropriate size (such as
tetras). Not mosquitoes, anyway, which attach to the surface film of
water. Cheers, Neale.>
Wormlike wigglers in cycling tank /RMF
Can you guys identify what these are?
They appear to be little white worms in the water but zoomed in they
look like larvae of some type. This is in a new setup about 4 weeks old,
no fish, fresh black onyx sand, RO water, and 81 degree temp. They seem
to have come out of no where. Thanks in advance. Video below image.
<Insect larvae... heads appear too small to be mosquitoes, maybe Midge
larvae. I'd net out, remove. Bob Fenner>
Re: Wormlike wigglers in cycling tank
Thanks for the reply. I added what is now a very full and satisfied
Platy to the tank.
<Heeee! I bet!>
The thing couldn't get to the little morsels fast enough. Happy to say
that all wigglers are gone.
<Cheers Mark. BobF>
I am not sure if you can help me or not, but, I found a strange
long worm in my pool. It appears to possibly be some kind of
parasite. Would you be able to identify it if I sent you a picture?
<Likely can help you narrow the ID down. Doubtful that this is a
parasitic species. Bob Fenner>
Here are some photos. I tried to send a video but I couldn't get it to
<Oh yeah... a horse hair worm, Nematomorpha/n... not to worry. BobF>
Re: Worm 1/20/15
Ok. Thank you. That's what I thought, but wanted a second opinion.
Strange worm in aquarium!!
Hello crew! It's been a few years since I've needed help from you guys.
My system isn't in need of help but I am hoping for
an ID on a strange worm.
So I was cleaning out an aquarium that has been set up for four months.
I am converting it to a Betta paludarium. Really
just an emergent/submerged plant set-up with
soil(Walstad). Anyway, while I was cleaning this tank out
I found about six of these worms crawling around
under the substrate.
This substrate is natural creek sand that I rinsed
and baked a few months ago(four as I stated
before!!). Anyway. After Initial l set-up I didn't
change anything except to move fish in and out of this system. I never
fed this type of worm. Just frozen
daphnia/flake/Spirulina flakes. I used local
<Ah yes; likely the source>
for this system so I'm sure that the eggs of these guys
somehow hitch-hiked in on the roots of some plants or,
something?! Anyway, Can you guys help me with an ID
and how do you think they survived for so many
<Yes; some sort of Oligochaete ("few bristles") segmented worm... same
group as earthworms, Tubifex, Blackworms. Not harmful. Thanks for
Tiny worm(s) 12/25/14
I checked the site and didn't see this little guy. It is living on a
fake plant in a ten gallon freshwater aquarium. Video attached. Happy to
have it if it isn't harmful but would love to have an ID. Thanks for any
<Some bit of fecal material. Bob Fenner>
"Poop of Earl" (sans soundtrack) >
little worm <not> in freshwater tank
Good evening! I would like to ask your help identifying a worm i found
yesterday. While cleaning out my tank, i noticed some little, very light
colored worms on my Anubias nana. I put them in a bowl for observation.
They didn't climb on the wall, just wiggled on the bottom. I haven't
seen them in my tank before, though they are small and my gravel is
light so i might have missed them. There were only a few. The body is
round, so i think it's not a flat worm, there was also some black
coloration on the head. I inspected the leaves and i found some brown
round things on one of the leaves, maybe the eggs or something? I took
some pics with my phone but they aren't the best, i don't have a camera
so i can't really make better ones, sorry. My questions are what is it,
is it harmful to my fish, do i need any treatment for the tank? My
friend suggested that i throw away my plants, but i don't really want to
if it's not necessary. I live in Europe.
<Likely these are aquatic insect larvae, possibly imported on the
plants, and in any event, almost certainly harmless. Nematodes
(roundworms) tend to be uniformly coloured (usually white) whereas
insect larvae (such as "maggots") have distinctive head regions that are
darker than the body thanks to their eyes and jaws. Hope this helps,
Re: little worm in freshwater tank
Thank you for your reply, I'm relieved. Than i go and replant my tank :)
<Most welcome, Neale.>
reddish leech looking creatures in my yard
in the last week we have found 2, 2inch dark reddish, skinny
leech looking things in my back yard. we don't have grass in my
yard. its dirt. someone told me that its a parasite! never seen these
before and im worried. have children and pets. please help! thank you,
<Without photographs can't really be sure. Would also need to know what
country you're in, and what your local climate is like, because that
makes a huge difference to the sorts of animals where you live. You're
not at all clear where you found these parasites; we're "experts" on
ponds perhaps, but not lawns, patios, or other sorts of garden features.
But as a rule of thumb, if the "something" is big enough to see easily
and just lying around in an obvious way, it's not a parasite. Parasites
are mostly tiny (even microscopic) because they need to get inside their
hosts, or else secretive, like bedbugs and leeches, because they need to
creep up on their hosts. The organisms you've seen sound much more like
earthworms, freshwater leeches, or possibly some sort of large insect
larva (such as Leatherjacket larvae). There are of course parasites that
affect dogs and cats, notoriously Lungworm here in the UK at the moment,
but the parasites themselves are essentially microscopic and transmitted
via snails and slugs
(which are in turn infected by faeces from an infected dog). You should
get yourself aware of the local parasites that pose a risk to your pets
by consulting your vet; they usually have leaflets in their offices
(detailing risks and symptoms) as well as suggestions on appropriate
preventatives and treatments. With regard to children, we're obviously
not medical doctors so refrain from giving you advice here; if you are
concerned, photograph the suspected parasite, show it to your general
practitioner and act accordingly. Cheers, Neale (who's merely a doctor
Re: reddish leech looking creatures in my yard
Thank you for your reply. If I see another one I will take a picture and
send it to you. And I live in Laplace Louisiana
<Glad to help. Neale.>
water worm 6/29/14
can you identify this worm and let me know if it is dangerous? I
found it in my swimming pool
<It's an errant Polychaete of some sort, and no, not dangerous. Any idea
where it came from? If the pool is outdoors and near the sea, that's
presumably where it came from, possibly dropped by a passing seabird.
Cheers, Neale.><<Well-done Neale. RMF>>
Worms of some sort, in turt sys. 12/11/13
I have a freshwater tank with 3 red eared sliders in it and I went and
vacuumed the water and then as I refilled the tank I saw some
red squiggly crazy freaking out worm with a type of pincher at the tail
end and a mouth that looked like it was unhinging
<... not an Oligochaete>
or somewhat snake like as it was eating the floating crap that I stirred
up when cleaning and refilling.. then I noticed with a closer look that
there are a bunch of way smaller worm like things swimming around in
there as well. These ones are harder to see because they are so small
but are doing the same thing the big red one does, as in squiggles
around completely looking like a crack head freaking out. Will these
things hurt my turtles? I've attached a video of this crack head worm..
<Mmm, from your description these are likely some type of insect larvae
rather than worms... But the latter are a possibility as well (from live
foods, plants... see Darrel's rec. re "Koi" pellets as a standard
At any length, neither are harmful to turtles... Read here:
and the linked files above. Bob Fenner>
white worms in water... using WWM
I just did a water change today and noticed a whole bunch of tiny grey
squiggly worms in both the dirty water I gravel vacuumed out in my pail
and in my aquarium water. what are they and are they good or bad there
in my aquarium? if bad how can I get rid of them?
and the linked files above... or... use the search tools on every page.
worms, FW ID 8/19/12
I have a question for the freshwater entomologist :
<Hmm… not exactly come to the right place!>
The other day I was watching a shrimp eating a dead shrimp. I guess it's
normal for a shrimp population to somewhat control itself ?
<For sure. Or at least, to recycle calcium from moults or corpses.>
The number of shrimps seems to stay about constant but I don't see very
many babies nor very many grandpas and grandmas.
<Pretty much true.>
Anyway, right near the dead shrimp I noticed a red wormy-looking thing.
I've never seen this thing before. It was about the size and color of a
bloodworm but not segmented.
<If it isn't segmented, it can't either [a] an insect larva such as a
chironomid larva; or [b] an oligochaete such as Lumbriculus.>
Also, it slithered over the rocks rather than doing the bloodworm
<Gliding over solid surfaces is more typical of flatworms, i.e.,
As I watched, it slithered away into the substrate never to be seen
again. The substrate is round river rock of various sizes. Not too big
but larger than normal aquarium gravel. Kuhli loaches love it. This
thing was slithery like a slug, not free-swimming at all and rounder
rather than flatter.
<Again, suggestive of a planarian.>
I searched the site and found Planaria and leeches but this creature
seemed more evenly shaped than a leech, not fat in the middle with
<Leeches are segmented; they are of course Oligochaetes.>
And it didn't have the triangular head that Planaria have.
<Ah now, the triangular head with the two eye spots is not universal to
I searched and searched the rest of the tank but only see/saw the one.
Any ideas what this thing could be ?
<Does sound like a planarian; look at species such as Dugesia which are
fairly common in ponds and get into aquaria via plants and live foods.
They're harmless, by the way.>
<Most welcome, Neale.>
Re: worms, FW ID 8/19/20
Thank you for the reassurance :)
They sure look nasty icky slimy but we probably aren't very attractive
to them, either …
I'm sort of assuming that since this is part of life, as long as they
aren't parasites they're actually good for the tank ?
<Or at least neutral. If you have a lot of them, then that tends to
indicate the tank isn't clean (overstocked, uneaten food, inadequate
maintenance). But a few of them is normal, and in some tanks adds to the
charm of the aquarium. Indeed, I have an 8-gallon aquarium on a sunny
windowsill that's crawling with tiny life such as these worms, and it's
a useful place to grow on small fish like Ricefish fry that feed on
algae and tiny animals. It's a fun tank to observe, almost like a reef
Especially since I've only seen one, not thousands ?
thanks again much :)
Tiny white worms 2/5/12
I am not sure if you can help me but there seems to be some tiny
little white worms crawling on the glass of my yabby's tank.
I have attached a picture (not so clear).
Are these harmful at all to the fish and to yabby?
<Not likely; no. Their sudden appearance is not uncommon. With
regular maintenance, being careful re feeding, they will just as
Your help is greatly appreciated.
<Read here: http://www.wetwebmedia.com/FWSubWebIndex/fwwormcompf.htm
and the linked files above. Bob Fenner>
Crazy little pink worms --
Hello, WWM Crew!
I have a question about my desktop 1.5 gallon planted Betta bowl
with blue aquarium gravel on the bottom.
I live in Phoenix, Arizona, and I used local tapwater with BIO
Safe and BIO Coat for water conditioners. I noticed a couple days
ago that my 2 year old pet-store bought Betta was acting very
funny. I figured it could have been a swim bladder issue (common,
first time with him, not my first rodeo with the beast), but as I
looked closer, I notice a swarm of flesh-coloured roundworms
swimming throughout the water.
<These are segmented worms... Annelids>
They're a variance of sizes (1mm - about 15mm at the
longest), and are not larvae of any of the common office--wide
annoyances (all 3 parents are entomologists. I had a fun
Now here's the thing, I know they're not Planaria. Like I
said, these are roundworms who kick and swirl around like
miniature young Tubifex.
<Do look like Tubificids to me>
I was raising some Tubifex in a 2.5 gallon at home, but I never
cross-contaminated these tanks.
They don't breathe air. I believe they're too small to be
hookworms. I can't get a good enough picture, but they're
long, thin, hairlike, at a variety of height levels, seeming to
prefer inhabiting my java ferns near the bottom. You can kind of
see them wrapped around one of the roots in the pictures. They
were flailing too much to get a good look at their head. They
don't crawl on the sides of the glass. When I remove them
from water, they turn light pink.
I cleaned his bowl thoroughly, was unable to remove the
infestation, tossed the rocks, rinsed again, replaced the gravel.
Then, as I was washing the java ferns, I reinfested that bowl,
so, I'm letting it dry out. Meanwhile, my poor old Betta
passed away (in a cleaner, different bowl, sand bottom). I got
new plants, and it seems that I managed to move my Betta to the
new bowl without cross-contamination, so it would suggest that
they are not parasitic in nature to fish. I still have the old
java ferns in a paper cup, and hope to eradicate them with an
Any idea as to what they are?
Also, is there an invertebrate killer that is not harmful to
<Read here: http://wetwebmedia.com/FWSubWebIndex/AnthelminthicsFWF.htm
Not worried about killing fish. These little guys will go in an
uninhabited tank until these things are gone.
<And here: http://wetwebmedia.com/FWSubWebIndex/bettasysart.htm
Re: Crazy little pink worms
Thanks for your answers! I've only ever taken java ferns from
this Betta bowl home, never the other way around. Such a mystery.
It's quite possible a Tubifex egg sac ended up in my bowl via
tap water. I have since switched to our filtered water. I could
do without another unintentional worm outbreak.
I've been thinking of getting a Picotope for my desk so I can
keep a filter and heater; currently, there hasn't been any
room. I guess it's time.
<Thank you! BobF>
Worms in my tank! 5/29/16
Hi, I have found a heap of tiny thread like worms in my freshwater
They seem to be float/swimming around in the water but haven't seen any
on the glass. In the water they look white but when I get them out of
the water they turn pink/red. I'm worried they are detrimental to my
fish and/or tanks.
<They are not.>
I've searched your other worm related articles but ant seem to find a
description that fits. I have attached some photos below. If you are
able to help me understand what they are and the dangers of them in my
tank I would be very appreciative!
<No danger at all. But do indicate surplus organic matter for them to
feed on, whether directly or via the microbes acting as decomposers.>
The tanks they are found in house Bristlenose catfish, and various other
L number catfish so the tanks can get quite messy between cleans (each
weekend). Thanks in advance for any and all advice!
<Answered your question right there. I'd ignore them, but I'd also keep
a better grip on tank cleanliness, so that over time the populations of
worms declined. Too much organic matter in the tank means your filter is
having to work harder than it should, and nitrate levels are going to
end up a bit higher than they would otherwise. Cheers, Neale.>
Re: Worms in my tank! 5/29/16
Thank you VERY much Neal! I was starting to panic.
The tanks that house the catfish are my two bottom racks so gravel vaccing
is always difficult using traditional gravity fed vacs but I do use the
Eheim quick vac pro that is battery operated
<Never found these much use, to be honest.>
and 50% water change each Saturday.
<Much more useful.>
I may need to look at how my tanks are set up and remove the messier cats to
a higher tank to make gravel cleaning more effective. As long as I know they
are not something harmful I can deal with this. Thank you very much!
Worm, Larvae, or other? 3/14/16
Just finished cycling a Fluval Edge 6 gallon aquarium after 4 weeks. I
cycled with pure ammonia from Dr.Tim's Aquatics dosing 4ppm each day the
ammonia read 0ppm. The tank is planted with Helianthus Callitrichoides,
Lilaeopsis Brasiliensis, Vesicularia dubyana, and a few Aegagropila
linnaei. I dose with Flourish Comprehensive weekly and Flourish Excel
daily with 12h/day lightning by means of my Finnex Planted+. The plants
growing wonderfully. There are also some snails that hitched a ride on
the Java Moss
I purchased from my LFS
, which I don't mind at the moment.
I have yet to perform a water change
and will do so after I figure out what these pests are. First here are
the water specs to get an idea of the conditions:
NH3, NO2 0ppm
NO3 80ppm (as I said, have yet to do a water change
<Who? The worms I'll assume.>
have definitely proliferated in the past few days (probably due to
increased nitrate concentration), with most coming out at night and
wiggling erratically at the top of the tank. Few also float in the water
column during the day. The majority are translucent with some varying
with brown specks. The supposed worms appear to be segmented, which
leads me to believe they are of the Annelid phylum or are larvae of some
and therefore not Planaria, but then again I could just be seeing
Maybe they are some sort of Dipteran larvae?
<Can you send along a well-resolved pic? The two groups of
invertebrates can be discerned on close inspection>
Please let me know!
<Please read here re identifying these groups:
Re: Worm, Larvae, or other? 3/14/16
Oh yes! The most important part of the email was omitted! Here is a
<Ahh; these appear to be insect larvae. I'd vacuum the gravel to remove
them. Bob Fenner>
Re: Worm, Larvae, or other? 3/14/16
Thanks for the help IDing them! I am planning on getting a school of 6
cardinal tetras, so I hope they will find them to be a delicious
<Which? I'd remove the larvae as stated... They may turn out to be fish
eaters, or flying about your house... BobF>