FAQs on Freshwater Worm (Flukes, Roundworms...)
Parasitic Diseases 2
Nematodes, Flatworms, Anchor
Worms and Other Worm Parasites of Freshwater Fish by Neale Monks,
Freshwater Diseases, FW Disease Troubleshooting, Ich/White Spot Disease, Choose Your
Weapon: Freshwater Fish Disease Treatment Options
by Neale Monks, Invertebrates for Freshwater
Aquariums by Neale Monks,
Related FAQs: Worm Parasites 1, Freshwater Worms, (Freshwater Worms of All
Kinds): & FAQs on: FW Worm Disease
Diagnosis/Identification, FW Worm
Disease Treatments, & FAQs on Parasitic Worms by Group:
Platyhelminths/Flatworms: ( Flukes,
Planaria, Tapeworms and Leeches), Acanthocephalans, Nematodes/Roundworms (e.g.
Camallanus),... Anchor "Worms": See FW Crustacean
Parasitic Disease, & Aquarium
Infectious Disease, Freshwater Fish Parasites,
African Cichlid Disease 1,
Cichlid Disease, Ich/White Spot Disease,
Need help with a fish problem 4/23/20
I’ve got a problem with one of my wagtail platy’s. Well, I say problem, it’s
dead and I’m not that up to speed with bringing things back from the dead.
i woke up on Monday morning too see it was dead, but there was this huge
parasite looking thing coming out of it. I’ve called 5 different places and
they don’t really have an answers. Made an account on Fishlore.com to see if
they have any answers. They had none. But someone said I should email you
and see if you have any answers I’ve attached a picture to help.
I've been keeping fish all my life and I’ve never had this before.. all
parameters are fine and well within range.
it’s belly was bulging so I thought it was pregnant, I’ve had lots of fry in
This thing wasn’t coming out of its gills or through its butt, it was come
out the side of the fish just behind the gills. It’s the black dot on side
of the fish just behind the gills.
I hope one of you lot can help me diagnose/identify what on Earth actually
happened, because I’m seriously stuck here. PS, I apologise for the fact the
picture was taken on an Easter egg box.. it was the first thing I had on
hand. Didn’t particularly want to handle it too much because a lot of
parasites can jump species
Cheers for reading, I hope you can help
<Evidently some sort of 'worm'. The problem is that it's hard to say whether
we're talking about an external parasite (which may not in fact be a true
worm, but a crustacean of some sort) or was this a worm inside the fish that
somehow got out through the wound. Very difficult to be sure without
actually having the fish in front of me, together with a decent dissecting
lens. In any event: certainly a good idea to treat your fish with
Praziquantel (such as PraziPro) or some other reliable anthelmintic.
Internal worms are quite common in livebearers, though rarely anything like
this. It's worth repeating the course after finishing the first course
because worms are difficult to shift. External parasites, particularly
crustaceans, are rare in aquaria and difficult to treat. Mostly, they can't
complete their life-cycle in aquaria, but some, notably Lernaea ("Anchor
Worm") can. Anchor Worms are distinctive because they have a dark, often
fork-shaped attachment head that digs into the flesh, as well as a
semi-transparent worm-like body that is visible outside the fish, often with
two egg-containing structures dangling even further. My gut feeling is that
we're dealing with something along those lines; if not actually Lernaea,
then some sort of crustacean external parasite. Cheers, Neale.>
Re: Need help with a fish problem 4/23/20
That’s absolutely fantastic! Thank you so much for your help, I’ll start the
treatment right away!
<Glad to be offer some tentative help at least.>
Goodness you guys are good.
<That's very kind. But do check your photos against pictures of Anchor Worms
and suchlike, and see if it is a plausible explanation.>
Well you’re definitely better than the 7 fish shops I’ve emailed and the 4
different forums I’ve posted on.
Can’t thank you enough for that!
<Most welcome. Cheers, Neale.>
Re: The (Pen)Ultimate Thread---Stocking 105 Gallon Semi-Aggressive Community:
NOT: FW worm concern 8/16/15
I have been feeding the blue Acara two kinds of medicated food: a frozen one for
marine fish with Praziquantel, and the other with IH-lmidazole (it is New Life
Spectrum Hex Shield pellets). I also have fed them Hikari seaweed pellets.
They like the frozen food, but the NLS Hex Shield they find unpalatable.
While they have gained weight, now they have something white protruding from
their vents. I suspect it might be an anal prolapse, (I normally feed my fish
algae-based food, but neither of the medicated foods are this, so I suspect they
are constipated.) If it is a worm of some sort, how would I tell?
<Camallanus worms tend to wriggle and if you tank a photo and look close up, you
may even see worm-like features. I agree with you, that the combination of
parasites and the medications might be irritating the anus causing it to stick
out. Should recover if all's well.>
Also is it safe to use Epsom salts with Zeolite?
<Yes. Cheers, Neale.>
Re: The (Pen)Ultimate Thread---Stocking 105 Gallon Semi-Aggressive
Do you have any recommendations for deworming medicines for the blue Acara? I
have heard some types can kill small fish, and these guys are pretty small now.
and the linked files above. Search ahead of writing us. Bob Fenner>
cardinal tetras with clear blisters and tiny white worms
I have a planted 13 gallon tank....well established for 2 yrs. 2
of my 7 cardinal tetras have developed clear bubble like blisters
(mostly near their pectoral fins and mouths). On close inspection there
appear to be tiny white worms within or just adjacent to these blisters.
My other species (Ram, Corys, platy) are unaffected.
<Mmm, could be... Nematodes, other>
Others have posted about this problem on other websites but there are no
definitive opinions on diagnosis or treatment. I am suspecting
they are tiny roundworms. It is interesting that this seems
somewhat unique to cardinals.
Any suggestions would be appreciated. If I can get a good picture I will
<If you can, please do>
<I would try introducing an anthelminthic via foods... lacing ahead of
offering. Okay for all to consume. Likely Praziquantel would be my/your
first compound to trial. Bob Fenner>
Free Living Nematodes Dangerous to Humans? 6/26/12
Hi There. I am working on eradicating a free living white nematode
population in my freshwater snail tank. My questions is: Are they
dangerous to humans? I'm usually quite careful to wear gloves when
I clean the tank, but today some tank water (with nematodes in it)
splashed on my leg. I shave my legs, so I might have some
Any advice would be greatly appreciated!
<I very much doubt there is, or will be an issue here. Human parasitic
Roundworm issues are principally a matter of ingestion (eating,
drinking)... the few burrowing types (e.g. swimmer's itch) involve being
in infested water for extended time... I would not worry. Bob Fenner>
Re: Free Living Nematodes Dangerous to Humans? 6/26/12
Thanks Bob. I appreciate your quick response!
<Ahh... we don't post our "classes attended" to our bio.s on WWM, but I
had two semesters of Parasitology and some related med. classes (e.g.
histology), and have had an earnest interest in such matters in the
intervening decades. IF you are truly concerned, I would consult w/ a
(likely tropical) medicine specialist. Cheers, BobF>
Re: Black moor with digestive troubles--
Well, it has been several weeks now and my poor little moor is hanging
in there but is still not well.
Its colour has faded and it has ongoing motility problems. It swims
normally for a few seconds, then swims backwards in a strange
"hiccoughing" motion. It is still extremely constipated,
presenting with long, trailing feces, some of which is so fine it looks
like a single strand of cobweb.
<Mucous perhaps? Or a single fine worm, e.g., a nematomorph?>
Metronidazole-based food did not work, nor did Praziquantel-based food,
peas or abstaining from treatment. Not surprisingly, it is beginning to
have flotation issues.
I have located a de-worming flake food that contains Fenbendazole at an
online store called Angelsplus.com. You suspected this fish was
infected with helminths and I think that it might be prudent to try to
treat for this now before I lose this little fish. I wanted to pass on
the name of the webstore (as long as it doesn't violate some rule
of your website) because it is the only place that I found that carried
a Fenbendazole-based food: hopefully this information might help
someone else who is having similar tank troubles. The company is based
in the US but they do ship to Canada (I'm not certain about the
<Thanks for sharing this information.>
I have not been able to use a microscope at work so if this fails my
next step will be to have the fishes feces tested for parasites. This
is an expensive option that I am hoping to avoid. I will let you know
if this food works for the moor or not.
<I'm actually very impressed by your care here; most fishkeepers
would have called it a day with this Moor, and either euthanised it or
simply ignored its problems.>
<Good luck, Neale.>
Re: Black moor with digestive troubles 3/20/11
I Googled "nematomorph" and discovered a whole new world of
things I'd rather have not viewed before breakfast! It could indeed
be a single worm- I have no way of telling without a closer look.
<Indeed, that is the case.>
It is so difficult to decide what to do or which medication might be
effective. <<None. RMF>> I don't want to kill the fish
by using too many medications. The fish also has a tank mate (who is
asymptomatic except that it has not grown since I purchased it as a
near-fry several months ago). The failure of this second fish to grow
does seem to indicate some sort of worm.
<Would seem likely.>
Do you think that a Fenbendazole food is the next most logical step?
What should I do about potential eggs or larva in the tank? I have
increased my water changes/vacuuming for this one tank to three to four
times per week since the fish has become ill- is this helpful? The
water changes are quite small as I don't want to disturb the
biological filtration. I have also been changing the carbon in the
filter once a week.
<If you're treating for worms, yes, it makes sense to treat the
Antihelminthic medications shouldn't affect biological filtration,
but do keep an ammonia or nitrite test kit to hand just in case the
fish start behaving oddly.>
I can't bear to euthanise since the fish are both still active and
interested in food. If this changes I will have to consider this option
but I am hoping I will be able to report otherwise.
<Good luck, Neale.>
re: Black moor with digestive troubles 3/20/11
Thank you! I have done some more "Googling" and found two
very good articles regarding antihelmith medications. The first is a
research paper comparing six antihelminthic drugs:
So I am wondering if Levamisole HCl might be a better alternative than
the Fenbendazole food since I need to treat the entire tank. Which led
me to the second article in a loach
However, I can't seem to find a supplier for Levamisole HCl in
Canada (since it is a cattle dewormer I find this odd- perhaps it goes
by a different name). I may be able to purchase from the US if it is
<Only Praziquantel and Flubendazole are sold over the counter in the
UK, and this may well be the same in the US.>
In your experience, what is the most effective treatment?
<No experience at all here! Never had to treat for worms. For
whatever reason, worm-infected fish do not seem that common in the UK
retail side of the hobby. I'm sure worm-infected fish do get sold
here, but compared to other sources of mortality, they just don't
seem to be significant outside very specific niches such as Discus.
With that said, products like Sera Tremazol, Solupraz and Wormer Plus
are sold/used here, and seemingly successfully.>
Re: Black moor with digestive troubles 3/22/11
I did find a supplier of Levamisole in the US so if the parcel
doesn't get stopped at the border I should have it in a couple of
weeks. It seems a long time for my poor fish to wait but it has been a
real trouper through all of this. I can only hope I am targeting the
right parasite/worm. I've ruled out Trematodes and Hexamita so
I'm keeping my fingers crossed..
In the meantime I am saving up for a decent microscope!
I will let you know what happens with the little moor.
<Thank you, and good luck! Cheers, Neale.>
re: Black moor with digestive troubles, Flukes
Sorry to bother you again, Neale (and WetWeb team):
Well, I have found flukes in all of my tanks- the highest populations
are in the tanks without UV sterilizers though even these have a few
rogue critters. As I mentioned, I cannot identify the exact species but
can say for certain that they are viviparous and I would like to try to
<Indeed.><<and, very common w/ goldfish in most places in
the world. RMF>>
I understand this is quite difficult and involves prolonged
<Can do. Otherwise, best to remove your fish, bleach what you can,
discard the rest, and then cycle a whole new filter.>
Is there a safe and effective way to rid my tank of these pests?
<Are we talking about Flatworms (free-living Platyhelminthes) or
true Flukes (parasitic Platyhelminthes, Trematoda and Monogenea, on the
skin and/or internal organs of your fish, e.g., Dactylogyrus)?
Free-living Flatworms are extremely common in aquaria and pose no
particular risk, though large numbers of them suggest less than
pristine conditions in the tank. No treatment is needed. For things
like Dactylogyrus then the usual treatment is an anti-helminthic such
as Praziquantel, though a vet may well propose alternative, better
I would have to treat the tanks so anything that will not kill off the
filter media (but will eliminate all the flukes that are hiding in
would be best. Has anyone had luck with complete eradication?
<Praziquantel should not exhibit any antibiotic/antibacterial
Re: Black moor with digestive troubles, Flukes
Yes, I am 99.9% sure that these are flukes- they have a widely
segmented body and hooks at the distal end that they use to attach
themselves to debris in the tank while they twist around looking for
<So they are free-living? Not all flatworms are parasites.>
When they detach they move with an extension-retraction motion (sort of
like a caterpillar).
<The Monogenea have suckers and hooks around the mouth; Digeneans
typically have two "mouths", one the mouth itself, the other
a kind of sucker. In Digeneans, the life cycles are often so complex
they cannot be completed under aquarium conditions. I'm sure there
are exceptions, but these appear to be rare. Under aquarium conditions
-- as opposed to pond conditions -- the more probable
"flukes" are Monogeneans, which usually have a single host,
i.e., the fish in this instance. Dactylogyrus is probably the most
common. There are numerous treatments used on fish farms, some of which
may be applicable to aquaria, notably Praziquantel; do see a good fish
health book for details and arguments in favour of one treatment over
I can clearly see a developing fluke within the fluke. I have not found
them on my fish but will do more systematic sampling to be sure. I have
not taken gill sample for fear of damaging the fish (is there an easy
way to take a gill sample or swab?)
<Not on small, ornamental fish species.>
As I mentioned, I have not been able to identify this fluke from
resources on the internet. These creatures do seem to inhabit the
buildup in the filter and the annoying spots of brown algae that
occasionally bloom in my tank. Is there a species of free-living,
<All Monogenea and Digenea are parasitic. Free-living flatworms do
not have suckers, and typically glide across flat surfaces. Do also be
aware of free-living leeches, as opposed to parasitic leeches.>
I really do like the idea of cycling new media and cleaning the tanks.
I have just read that Prazi over a period of 21 days may be effective
but am loathe to medicate my fish for such a long period of time unless
Prazi is indeed safe for such a long-term application.
<About as safe as any medication.>
If I do opt for the first method, what is the best way to ensure that I
don't transfer a fluke to the new tank via the fish when I transfer
<You can't. By definition, a live fish can carry across
parasites, and indeed this is precisely why releasing Goldfish and
other ornamental fish into the wild is such a risk -- any such fish
could carry parasites from fish farms and/or the tropics into the wild.
Treating in a hospital tank with a Zeolite (non-biological) filter may
help break the cycle.>
re: Black moor with digestive troubles
Thanks again, Neale:
I will try to find a good book so that I can identify this fluke. It
most resembles the Gyrodactylus fluke but the distal end is different
(it does not have the polydactylous hooks). It also has a very
stalk that looks like the eyestalk of a snail or slug near the head. I
can't find this anywhere (ah, maybe I have discovered a new fluke!
The Monogenea Almedius..). At any rate, I will take some more samples
from my fish to see if I can find any on the actual body surface. If I
find out what this is (or if I can afford a camera attachment for my
microscope) I will send along the info!
What frustrates me the most is that this is my fault.. though I have
been very careful to quarantine new fish (I usually do so for two
months) I became complacent and began using the same vacuum on all of
the tanks near the end of my last quarantine. Sigh.
<Hello Gina. Thanks for the update, and I commiserate with the
feeling that you, the owner, have somehow created the problem
you're having to deal with. We've all been there. Life
doesn't have an Undo button unfortunately, so you have to live and
learn. Good luck, Neale.>
re: Black moor with digestive troubles. More worm spec., now Rotifera,
I have never been so happy to admit I was wrong! I have finally found
my creature- and it is NOT a fluke. It is, in fact, a rotifer. I
can't find the exact species but it is one of the Bdelloid rotifers
and looks very much like the Philodina gregaria (and is possibly a
I had identified other rotifers in the water (beautiful stentors and
other unidentified, round, fat rotifers) but I missed the cilia on
these ones as they move too much to be able to focus the scope. I found
one this morning that had the decency to die without contracting and
was able to zoom in it a bit better. This explains why I find the
greatest concentrations in the filter and why the "foot" does
not have the hooks typical of a fluke. They do look very fluke-like and
move in the same fashion so I can see why I got confused.
<I can understand the confusion, and I'm very pleased to hear
the good news. I will make the observation that excessively high
concentrations of any microbe, good or bad, could suggest issues with
aquarium cleanliness, so keep an open mind there.>
This just leaves me with nematodes to deal with in two tanks. I am sure
that won't be fun, either but at least I don't have to worry
about flukes at the same time!
<Indeed. Free-living nematodes aren't a problem, but Camallanus
worms are perhaps the most annoying of the parasitic forms found in
aquaria. Not too difficult to treat, but do bear in mind that carbon
and excessive amounts of organic material in the aquarium (silt, mulm,
etc) can reduce the efficacy of any medication. Cheers, Neale.>
re: Black moor with digestive troubles... Nematodes,
Ah, yes, I do think the nematodes I have found are of the free-living
sort as they are found in scrapings from the inside of my filter. They
most closely resemble "vinegar eels" though I have not found
them swimming in samples of tank water, only in filter detritus.
<I see. Harmless.>
I have taken dozens of samples of fish waste and have not found any
worms with the exception of one sample I gathered from the bottom of
the tank that I suspect had been sitting there for a few hours and had
been infiltrated by the worms. The rest of the samples have been more
This is both good and bad as this means that I have failed to identify
the trouble with my poor little moor (which is still alive but not very
<May simply be poor genes or some other syndrome we can't
identify or treat. Just as humans have hundreds of different diseases,
so too do fish, and as hobbyists we are only familiar with a few of
I did find one evil-looking nematode with a stylus but this was in my
Oranda tank and I have not been able to find another. Samples of my
Oranda's waste has some sort of very small worm (?) or other
creature that I cannot identify as it is very hard to see even at
1600x. This may be normal- I can't find any information on the web
about what normal fish poop should look like under a microscope!
I do very regular maintenance on my tanks- I do small water
changes/vacuuming a minimum of twice a week and I change the filter
pads or squeeze out the sponges every 4 to 6 weeks. Perhaps this is not
enough- should I adjust my filter maintenance, perhaps?
<This does all sound adequate.>
My fish are fed home made gel food which is made of a large variety of
blended vegetables and Spirulina algae- I don't put it into the
tank directly, I have, ah, trained my fish to take bits of food off of
spoon. I didn't think there was excess food left in the tank but
perhaps small bits are escaping. This would be great fodder for
nematodes and rotifers I should think.
<Likely so, but in itself, not a problem. Most, likely all, tanks
have some sort of microbial fauna, and this plays a key role in the
biological filtration process. Without them, the solid wastes from your
get broken down into the particles and dissolved chemicals your filter
Anyways- thank you so much for your help, Neale. It has been quite a
journey trying to save the black moor: I guess part of trying to find
the source of a problem is to rule out what isn't a factor!
<Glad to help and listen. Cheers, Neale.>
Help with a worm issue please
My Husband went home today and found our Goldfish dead. There was a
worm that was working it's way out from inside of the gill. It was
as wide as a pencil eraser, It was white with reddish orange, maybe an
inch long but it was coming out of the gill and then going back into
the fish through his side. VERY nasty!!! What is this? I have 3 other
fish in the tank. A catfish and 2 black goldfish. Do you think they are
<Possibly. You will need to use a proprietary anti-helminth
medication since there's a chance the other fish are carrying worms
Medications that contain Levamisole, Piperazine and Praziquantel are
often recommended, but they don't work reliably, so if you can, use
medications with Fenbendazole or Flubendazole instead. Do also be aware
that some crustacean parasites, such as Anchor Worms and Gill Lice can
look worm-like at first glance, and nothing you have said here helps me
identify the problem either way, so you should use a search engine of
your choice to find photos of these, and then act accordingly, since
different medications will be required. Do be aware that some
medications can be toxic to catfish, and do also remember that
parasites often become problematic only when the fish are stressed, so
review environmental conditions. Three Goldfish would need 40 gallons
or more, and big catfish, such as "Plecs" (usually
Pterygoplichthys species) can't be kept safely in tanks less than
55 gallons in size. So if you have a small tank, less than 55 gallons,
environmental conditions could easily be part of the problem. Cheers,
Worms, Constipation or Dropsy? 6/9/09
My 13 year old son has a Columbian Tetra
<Is a very social species... not well kept singly... needs to be in
a group... but in a larger system as well than I read you have
with some problems. We are fairly certain he is a male. A few days ago
we noticed it looked as if he swallowed a marble as he bloated up very
quickly. He is acting almost normal - a little lethargic, tends to swim
away when approached, breathing a little more heavily. He was on a diet
(almost entirely) of flake food.
<Ahh! Likely at least a good part of the issue>
I suggested feeding some shelled, green pea,
<Look to Brine Shrimp, Daphnia...>
thinking he might be constipated. He did eat a little. He has continued
this way, neither growing slimmer or fatter for 5 days now. We have
halted the flake food, and are only offering pea, which he does not
have too much interest in.
<Would you be? Not I>
He does not appear to be pineconing, but yesterday I noticed he had a
bright red "tread" coming from his anal area. It is quite
long and stringy - with no stiffness to it (i.e.: free flowing - like a
polyester thread as opposed to a hair). At first I thought it was a
constipated poop, but it hasn't changed (dropped off) in a day.
He's in a 10 gal tank with another Columbian Tetra, 2 harlequin
Rasboras and a shrimp. Everyone else appears o.k. I hope my
descriptions help as I'm not entirely sure we're dealing with
worms here. Any thoughts or ideas?
Thanks very much,
<Again, the crustacean food/s (frozen/defrosted is fine) are your
best route here to mix in regularly... as laxative. Bob Fenner>