Anchor worm (aka Lernaea) is a goldfish illness that is usually caused by live feed.
What are anchor worms? Anchor worms are parasites that embed themselves into the flesh of your goldfish (or other freshwater fish).
When visible they appear as pieces of string between 5mm and 10mm with a forked tail embedded in the goldfish's skin. It may also appear from open sores, blood spots or red rings. Anchor worms are clear/white, red/brown or green in color.
What is the problem with anchor worms? Anchor worms can seriously harm your goldfish and even kill them. The wounds caused by the worms infect, causing other diseases that will kill your fish eventually.
What are the symptoms of anchor worms?
- Scratching by rubbing against objects in your tank. This behavior often occurs before the anchor worm is visible.
- Threads hanging out of your goldfish's body (see picture above)
What is the best treatment for anchor worms?
All good pet shops stock remedies for anchor worm. Treatment for this goldfish illness is usually complete within 3 - 4 days. It is important to note that some treatments are based on inhibiting the formation of insect exoskeletons, and therefore may have wider implications in ponds than in aquariums.
Potassium Permanganate is used to treat anchor worms. Add 2 mg for every liter water in your tank (it will color your water).
Another method of treatment is removal by tweezers, but I recommend the potassium solution.