What Are Camallanus Worms?

So your fish have red worms sticking out of …..

A Customer’s experience of Camallanus worms

Recently, I have heard stories from customers about red worms protruding from their fish cloaca’s or anus. These red worms are called camallanus worms, a parasitic nematode. These nematodes are extremely contagious and should be dealt with when sighted. By the time you have noticed them the worms will have already been in their reproductive stage and may have released microscopic larvae into the tank. Here is one woman’s experience of diagnosing and treating this parasite that has been infecting people’s tropical fish. Hopefully her experience will help others.


  • Aquarium:  setup in our insurance office, well-planted (with co2 diffuser) 29-gallon freshwater tropical, checked daily throughout the day when we need a moment’s break from work, and carefully in the evenings 6 days per week while feeding. Both of us who work here are very attached to the fish, and count them daily and keep track of who is looking old, acting different, etc – BTW all the fish had names and we could tell them apart.

  •  Fish: female betta fish, medium pleco, assorted platys, tetras (cardinal, neon, black phantom, lemon), dwarf neon rainbowfish, harlequin rasboras. Well-established for one year with no previous outbreaks of any sicknesses – fish have only died from what appeared to be age (i.e. they slow down, look a little ragged, and after a few weeks they disappear). Very stable pH and nitrites, measured approximately once per week plus whenever any fish acts strangely. I had almost never had to net out a fish as they are eaten by the others that quickly. Has that ever changed now!

  • History: Several months ago, my female betta fish had swelling in her ventral area, followed by a small red thread-like projection from her anus. Internet searches didn’t show anything up and she acted normal, so I eventually assumed it was some kind of weird hemorrhoid and figured either she’d make it or not. I didn’t realize it might be contagious since no other fish had any signs. A few months later, several other fish suddenly had the same problem, so I knew it was some kind of parasite and they had all incubated in the same time period (and by then, the betta had many of them protruding from her belly).

  • Treatment: First I tried Clout but saw no change, so I tried a formula of fenbendazole developed by a veterinarian hobby aquarist, which worked! Sadly, it was too late for many of my fish, and they perished from after-effects of the worms, but the fish in my home aquarium (set up in December with water from my office aquarium) have survived as they didn’t have time to develop as severe a worm burden as the ones at the office. When there is a severe worm burden, the worms might decay inside the fish, causing all sorts of problems and eventually killing the fish, even though it survived the treatment itself and the treatment “worked” by killing the worms. This medication is not particularly harmful to fish — though it might kill your snails… I had tiny ruby ramshorn snails (volunteers) and have vacuumed out many shells during the past few weeks, but it apparently does NOT kill their eggs, as I am now seeing new snails. The magical formula is fenbendazole in granule form: dissolve 3 ccs of the granules in 100ml of water (I find it dissolves best in hot water with vigorous stirring). After it is well-dissolved and the water is back around room temperature, soak whatever amount of frozen bloodworms or brine shrimp that you would usually feed your fish in this cloudy water for 30 minutes. My fish were just as excited to eat this food as non-medicated worms & brine shrimp. You can dump the food and medicated water straight into the aquarium, or you can strain and only feed the worms or shrimp. The key is that they have to eat food with the medication in it. Within 24 – 36 hours you will see that the worms turns grayish and die. Not all worms will die, but many or most will die with the first treatmentIt was recommended to follow-up with a second treatment in two weeks, which I did, and have not seen a single worm since that second treatment. YAY!

  • Follow-up to Treatment: It is very important to feed your fish well after each treatment, to help their digestive systems expel the dead worms in a timely manner, thereby preventing stress that can open them up to opportunistic infections, let alone septicemia which can result if the decaying worms remain in their bodies for too long. Considering this, it is actually better that the worms die in stages with the two treatments, rather than all at once. You can feed them their usual food, but try to feed them any roughage that they will eat. My fish happen to adore sinking algae pellets even though they are top-feeders by nature, so I gave them some pieces of algae pellet twice a day. Another excellent food is peas (yes, green peas). Remove the soft centres from peas (fresh or frozen, obviously make sure to avoid artificial additives) and cut or mash them up. Regardless of the type of food, be sure to feed twice a day and watch them closely for signs of stress or secondary issues so you can take action (melafix, salt treatment, or whatever is appropriate). Repeat the fenbendazole treatment after two weeks to be sure to kill all worms.

  • Source: I had no trouble securing this medication from a local veterinarian, Tsawwassen Animal Hospital (they started a file for my fish as it is a prescription). It is marketed as “Panacur” granules for de-worming dogs and puppies, and they also provided a small syringe to help measure out the 3ccs of granules. It cost around $15 for enough to treat my office and home aquaria. I hope that our somewhat sad experience will help others to combat this horrid nematode on first sight, which gives affected fish the best chance of survival and continued good health. At this point, I have the pleco, some platies, and the dwarf neon rainbowfish left, and we are still battling finrot and some kind of secondary infection on the pleco’s back. The tank looks so sad and empty, and I look forward to the day when I can once again watch my fish enjoy a healthy and vibrant home.

Thank you Danielle Bujnak for sending me your story.

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