That Fish Blog – Aquarium Advice and Information
Hello, Frank Indiviglio here.
Anchor worms are crustaceans (specifically copepods) and as such are more closely related to shrimp than to worms. They often make their presence known in outdoor ponds as winter turns to spring. Lernaea elegans, the most commonly encountered species, remains dormant during the winter and becomes active as the water reaches 55 F or so.
Identification
Anchor worms bury below their host’s scales, but betray their presence by trailing ¼ to ½ inch-long portions of their black, thread-like bodies from infected fishes. They usually attach about a fish’s gills, eyes or fins, but can occur most anywhere. Other signs include inflamed or raised scales and efforts by fishes to dislodge the parasites (leaping, rubbing).
Infestations most commonly occur during the spring, when the parasites are searching for new hosts after their winter dormancy. Conveniently for the anchor worms, the immune systems of pond fishes are at their weakest at this time, having been stressed by cool temperatures and the long winter fast.
Secondary Bacterial Infections
Anchor worms rarely cause fatalities, but the wounds they inflict frequently become infected by opportunistic Pseudomonas and Aeromonas bacteria. Ever present in the pond, these pathogens can easily kill fishes, especially those with depressed immune systems.
Avoiding Anchor Worms
Be especially careful to check for anchor worms when purchasing koi or goldfishes in the late winter or spring…those that have been wintered outdoors may be infected. They also parasitize weather fishes, channel catfishes, hi-fin loaches and other species commonly kept in outdoor ponds.
Anchor worms of various species can also be introduced to your collection via tropical fishes which have been raised outdoors.
Treating Parasitized Fishes
Fortunately, Jungle Lab’s Anchors Away is an effective treatment for infestations of anchor worms and certain other parasites. Be aware that this medication will kill crayfishes, snails and other invertebrates, and that carbon should be removed from your filter while treatment is ongoing.
It is also useful to add an ultraviolet sterilizer to your pond’s filtration system. UV sterilizers will kill anchor worms in the free swimming larval stage (they are not effective against adults), thereby preventing re-infestation.
Further Reading
A detailed article (Food and Agriculture Association of the United Nations) on the life cycle of anchor worms and related parasitic copepods is posted at.
Please write in with your questions and comments. Thanks, until next time, Frank Indiviglio.
Image referenced from Wikipedia and originally posted by Brian Gratwicke
I got some free koi from a breeder that were infested with anchor worms and I can’t seem to get rid of them. Treatment keeps them down but as soon as I stop they’re back. Could they be resistant to traditional treatments.? Help
What have you treated with and for what duration? You may need to use a stronger medication like anti-fluke, or it may be that you need to treat them for a little longer after they seem at bay. You may want to consider dosing with pond salt and investing in a UV Sterilizer if you have not already as another/additional measure once they are under control. It may also be a good idea to have some melafix on hand once the worms are dead to help heal the holes the worms have left so that no infections and ulcers develop. I doubt that they are resistant to the treatments, but the weather may play a role in how effective some medications are. The water temp should be >60 F for many meds to work reliably.
HI I WANTED TO FIND OUT IF ANCHOR WORMS COULD GO INTO CHILDREN THAT SWIMS IN THE POND WITH THE FISH.
I don’t think you have anything to worry about. Fish lice and Anchor worms are pretty specialized in the host and conditions they need, and fortunately humans are not part of their host repertiore, and should not be a concern. I have found no information on human anchorworm infections, and due to their need for aquatic hosts and conditions there is virtually no likelihood that that parasites could infect a human. If you are still concerned you may want to consult a physician.
Please help
I had an anchor worm problem this year with some of my
1-2″ goldfish that I had in a brand new 600 gal pond that I dug up this spring. I only had about 10 small goldfish in the pond, but the pond was drying up fast from the lack of rain this year 2012, so I moved the fish back into there 25 gal tank inside the house.
After about a month fish started to die, I had no idea what the problem was till there was only 3 fish left, then I started to look real close and that’s when I noticed the anchor worms, new to this problem I treated the tank with PraziPro, and took out the carbon out of the filter, but it was to late for the fish. 4 days later after I treated the tank I took the dead fish out and looked at the worms with a loop and I can see that some were still alive. My question is how long does it take for this product to kill the worm?
Also how does this parasite effect frogs and tadpoles in a pond?
And the most important question I have is
If children or adults are playing in a small pond like mine catching frogs and tadpoles that is infested with parasites/anchor worms and eggs and someone gets these parasites or parasite eggs in an open wound/mouth/eyes will they become a problem and how will it effect the human body?. Thanks Frank
Prazipro won’t be effictive on anchorworms…you’ll need a product like Clout or microbe lift lice and anchorworm treatment Anchorworms should not cause a problem for frogs or humans.
Anchor worms are a real problem in the fish business. It takes some strong chemicals and a long time to get rid of them. Tadpoles & frogs also can be infected with them and hop from pond to pond to spread them to other ponds. Humans as far as I know do not get infected. Max
It’s going to be end of mine day, except before ending I am reading this impressive paragraph to improve my experience.
any thoughts where the initial anchor worm or lice come from? is it from poor fish tank/pond water quality?
Hi Han, They are naturally occurring in most areas in natural ponds and streams. They may be introduced into artificial ponds through fish and plants harvested from natural systems.
How long will a anchor worm larvae live with out a host, can they be in my pressure filter and how long can they live in it if I disconnect it, also will they be in my Lilly plants if I take the Lillie’s out and transfer them to another holding tank
Hi Jason, Anchorworms will usually reach the parasitic phases in about a week. I wouldn’t expect them to live in your filter or in a plant without a host; they will only host on animals like fish (or occasionally amphibians like tadpoles).