Capillaria pterophylli

This week we take a closer look at the nematode worm Capillaria pterophylli, a highly pathogenic fish parasite. The presence of Capillaria in the intestines often leads to malnutrition of the host, the fish. This results in weight loss, a decrease in resistance to both infections and adverse environmental conditions, but also causes mass mortality of fish. All fish species in an aquarium can be infected with Capillaria, but the problem is most acute for discus, angelfish, catfish and live bearing fish like guppies, swordtails and platies.


Let’s take a look at the symptoms that fish show when infested with Capillaria:

  • Poor growth of young and adult fish
  • Skinny, sunken belly
  • The fish lose weight despite eating well and sufficient food
  • The fish lose their bright colors and become pale or darker
  • The feces of the fish have transparent mucous parts
  • Microscopic examination of feces reveals capillary eggs, which are brownish in color and have a characteristic barrel-shape with caps on both sides.


Sexually mature female Capillaria can reach 17 mm in length. Despite their length, they are very thin and difficult to see with the naked eye. The females produce eggs throughout the year. Capillaria eggs, along with fish feces, enter the water. Worm larvae develop inside the eggs. This development stage lasts 33 days. Fish become infected directly by either ingesting eggs or by ingesting intermediate or paratenic hosts, such as oligochaete worms.

For this nematode the prepatent period – which is the period when the parasite has invaded the host but the parasite is not sexually mature yet – is at least 3 months at a water temperature of 20 – 23 °C or 68 – 74 degrees Fahrenheit. When the water temperature is increased, this period may slightly decrease. From the moment a fish swallows an egg with a developing larva, it takes about 3 months before the worm reaches a sexually mature state.


eSHa -ndx will help to fight capillariasis in fish, but do not forget to take into account the life cycle and timing of the development of the worm and repeat the treatment every 2 weeks for a total of 4 times!

Would you like to contribute you own information based on experience to our article? Please use our contact form here, leave the info below in a comment or send us an email at


Share on Facebook
Share on Twitter
Share on Linkedin