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FAQs on the Flatworms that are Leeches!

Related Articles: Snails and Freshwater Aquariums by Bob Fenner,  In vertebrates for Freshwater Aquariums by Neale Monks, Assassin Snails and Sulawesi Elephant Snails. Keeping Clea and Tylomelania in the Aquarium by Neale Monks, Fresh and Brackish Water Nerites by Neale Monks, 

Related FAQs:  Freshwater Snails 1, Freshwater Snails 2, & FAQs on: Freshwater Snail Identification, Freshwater Snail Behavior, Freshwater Snail Compatibility, Freshwater Snail Selection, Freshwater Snail Systems, Freshwater Snail Feeding, Freshwater Snail Disease, Freshwater Snail Reproduction, Snails by Species: Mystery Snails, Malaysian/Trumpet Snails, Ramshorn Snails,


Unknown roundworm in aquarium     10/2/18
I saw this worm yesterday in my aquarium. Could you please help me identify it and whether or not I should get it out of my tank?
<Umm; nothing attached. No photo here>
It's currently in a 29 gallon planted tank with dirt (from a bag) and the tank is about a year old. The most recent addition in the tank was a pond plant. Could it have come in that way?
<Oh yes; roundworms, nematodes are VERY common; almost all are innocuous; not harmful>
It doesn't look segmented and seems to have a suction on one end (the back end). The back end doesn't look like an earthworm where it's tapered, but looks kind of blunt, like it was cut. I haven't seen it burrow into the substrate or crawl up the glass like other worms. It's brown and looks
"solid" rather than clear.
<Oh... this reads more like a leech, Hirudinean, rather than a roundworm; which are by and large smooth, tapered at both ends, light colored>
I've uploaded a video I took earlier today.
<Unfortunately this video isn't playing for me>
Hopefully the video is clear enough. It moves pretty quickly, but it's not shy. I could probably get another video or picture if you need it.
<Do please send the image, video link along>
Please let me know if you need any additional information.
<I'd be removing this worm>
Thank you!
<Thank you for sharing. Bob Fenner>
Re: Unknown roundworm in aquarium     10/3/18

<Hey Cath>
Thanks for getting back to me so quickly.
Sorry for the broken link. The video was uploaded as private, rather than unlisted.
Here's the new link: https://youtu.be/wd_PdDDcxLA
Please let me know if there are any problems with it.
<Oh yes; this is a Leech (yeah, yuck); possibly parasitic on your livestock. Remove it (w/ extreme prejudice)>
<Welcome! BobF>
Re: Unknown roundworm in aquarium     10/3/18

Thank you for the id.
So, if I'm looking at it correctly, the leech is moving backwards? It searches with the tapered end and uses the blunt end as an anchor.
<Hirudineans have "haptors" on both ends, and can move backwards and forwards using them and extending their bodies>
Thank you again.
<Certainly welcome. B>

Freshwater black leeches in tank      7/8/18
They must have come in on plants. I read that getting rid of them is impossible. Have been removing gravel, but eggs will remain?
<Hard to say.>
Never knew such a thing existed. Identification is definite: inch long extended, collapse to about half inch, black, hang on with mouth end, can wiggle through water but mostly hide.
<Do bear in mind many of the common leeches you find in clean freshwater are carnivores on small invertebrates, and pose no risk to fish. So there's no need to be completely paranoid about them.>
What do eggs look like?
<Varied; small, often nondescript; do see Google Images, re:>
Will my weather loach eat them, especially with less gravel for them to hide in?
<Yes, but I wouldn't completely rely on it to get rid of all of them.>
Any other fish eat them?
<Most fish that eat worms will eat leeches if they can.>
Also have mystery snails....will they be contaminated by them?
Any chemical solution that won't hurt snails, loach, tetra in tank?
<Anti-helminthic medications should work, such as PraziPro, but these may harm invertebrates such as snails and shrimps. I would remove the Mystery Snails to another container for a few days while using such medication.>
I really hate these creeps. Have gotten evil pleasure washing gravel in small batches in very hot water and watching dead leeches flow away.
<Leeches are important predators on genuinely annoying organisms such as mosquito larvae, with very few species actually posing a threat to humans, and even then, they're more of a nuisance than a health risk. Modern medicine doesn't use them as much as in medieval times, but they still have value in reducing certain types of swellings and inflammations better than anything else. So while few people want them in their fish tanks or ponds, they do deserve a bit of respect, even appreciation!>
But I know this is only reducing population. Does this harm eggs?
<Anthelminthics should handle worms and their eggs.>
Thank you.
B Burg
<Cheers, N Monks.>
Re: Freshwater black leeches in tank    7/9/18

You are awesome.
<Nice to know!>
Thank you so much.
<Most welcome.>
Yes, I am aware they can be very helpful in micro surgery cases. But I have watched/loved African Queen movie...
<Ah, great film.>
Again, thank you so much. Google actually confusing, could find no photos of eggs, much non-info.
<Oh? Well, simple small off-white to grey spheres, maybe 1 mm across.
Different for different species.>
Yours the best.
<Glad to help, Neale.>

The Fate of my Leeches  10/10/11
First I wish to say greetings to you from both my husband and me. We have both looked for answers to our questions on WWM over the years.
<Thanks for your kind words.>
Here is some background information: I have a 16 gal bow-front tank which has been set up for a few years. It contains cherry shrimp, class N Endler's, Hara jerdoni, Scarlet Badis, Malaysian Trumpet snails, and Tanichthys micagemmae. This tank also is thickly planted with various Cryptocorynes, Bolbitis heudelotii, and Windelov java fern (the latter 2 attached to African Mopani Root Wood). For filtration I use an Eheim HOB filter. I also use an air pump with airstone to keep oxygen levels up at night due to all the plants. I recently added a moss ball. As everything else has been in the tank at least a year, I am guessing that this may have been the culprit.
<Perhaps. Moss Balls -- if you mean those Cladophora colonies -- are coldwater algae, and as such, may be cultivated outdoors or in ponds. As such, they may bring in all sorts of pond life. They don't do particularly well in tropical conditions, and without constant rolling around like they get in the wild, eventually fall apart into some sort of mat or lump.>
Last month, I noticed a light gray "worm" of about 3" length and perhaps 1/4 - 3/8" wide swimming like a snake in the tank when the lights first came on by timer. It rapidly headed for the substrate and buried itself.
When I feed in the mornings (but not in the evenings), I occasionally see a portion of this "worm" sticking out and attempting to catch bits of food.
<Sounds like a leech!>
I feed New Life Spectrum small fish formula 0.5mm size, Fluval Shrimp Granules, New Life Spectrum optimum freshwater flakes, and live Daphnia (species unknown -- local culture I have kept going indoors for a couple of years). I have never seen any type of worm in my Daphnia tank.
Last time I vacuumed the gravel, two of these "worms" were left in the bucket and were attached at both ends to the plastic bottom of the bucket.
This is what made me pretty sure I had leeches. I attempted to take a picture then, but as my camera is of poor quality, the results were nothing more than a gray blur.
Now, here is the question: I find the leeches are pretty awesome. My fish all appear healthy and are eating well. My plants look fine. The shrimp are still reproducing. I actually enjoy watching these leeches move around in the tank (when I am lucky enough to see them swim) and I enjoy watching them try to catch bits of food. My husband is of the "EWW it's a leech!"
school and advises a full tear down of this tank to remove the offending leeches. We have 7 tanks total between us. This tank has its own gravel vac and siphon tubing and its own nets. We use one set of 5 gallon buckets for dirty water and 5 gallon drinking water containers for clean water. I don't see much chance of contaminating the other tanks with my leeches, but this is his worry. He is concerned that I will put leeches in our 125 gal Tropheus moorii Moliro Red/ Eretmodus cyanostictus Kapampa tank. My only real concern is for my Hara cat and my Badis. They both love to eat tiny live things and I am somewhat concerned that they could become ill from eating baby leeches.
<Most leeches are in fact free-living and feed on invertebrates. So things like bloodworms would definitely be on the menu! They may even scavenge to some degree. Some are blood-sucking on fish, but these tend to leave obvious wounds, often with a three-tooth bite distinctive to this group of animals.>
We have agreed that we will post this issue to WWM and proceed as directed.
Both of us respect your opinion on such matters.
Thank you,
<Without a positive ID it's hard to be sure. If this was me, I'd perhaps experiment first. Put them in a breeding net, and see if they eat wet-frozen bloodworms or krill. If they do, and seem to be free-living rather than parasitic, doing well for a few weeks under such conditions, I'd then maybe try them out in a tank with fish too large to be damaged.
But I'd keep a very close eye open for odd bite marks. Hope this helps, Neale.>

Ftn. leeches?? 12/17/10
I have found small red worms that strongly resemble ones discussed on these two pages http://www.wetwebmedia.com/fwsubwebindex/tapewmfwf.htm
in a freshwater outdoor water fountain (with no fish). When I go to change the water every other day or so they float up and are swept out of the fountain and into the flowerbed. Birds use the fountain to drink and I imagine that mammals use it at night. I have red wriggler earthworms and décolleté snails in the yard also, but never find them in the water fountain.
My questions are;
Are they harmful to birds, cats or skunks etc?
<Can't tell with the information presented... All Leeches are parasitic...
can't/don't live long w/o hosts. Do yours show segmentation, suckers?>
If they are harmful how do I eliminate them?
<Simple bleach>
Is it possible to 'dose' the water to prevent their return?
<Depends on the source...>
I don't currently have a pet but when I did she did drink out of the fountain, when I get another will I have to prevent it from doing this?
Thanks, Pam Kelso
<Welcome. Bob Fenner>
Re: leeches?? 12/18/10
Thank you for the reply. In rummaging around the internet after I sent this to you I think that I have identified the culprits. They are midge fly larvae, bloodworms.
<Ahh! Quite common to have such insects w/ aquatic larval stages using water features opportunistically. And not a disease issue>
Because I clean out the fountain every few days I never saw them at maturity and they were always small and non-segmented. I know that we have midge flies so I think that solves it. Thank you for getting back to me so quickly.
Pam Kelso

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