Anchor worms are commonly thought of as a worm, however, it truly is a large parasitic crustacean that attached itself to a fish's skin. The most commonly infected fish are those in which their setups are housed outside, such as with pond fish due to the parasite being able to move from locations during a rainy season. The most common traits that a fish will show when they are infected with anchor worms, is having the appearance of small, thin, white worms dangling from their scales.
Anchor worms are small little crustaceans that are free-swimming and search for fish to bury their bodies into. Sadly, anchor worms can cause serious damage if not treated at the first signs and are one of the most common killers of fish that are placed outside or with other fish that are transferred from different tanks often. This parasite itself can be seen by the naked eye and can reach in sizes from 10-12mm.
To understand how to treat anchor worms, we must first understand how they breed and in which stages that they can be killed off in. In the first stages of infection, the parasite will burrow its head into the fish's scales and dig itself underneath the scales and tissue of the fish. During this stage, only the body and tail can be visible as they are still hanging outside of the fish's body. As the parasite grows, it will reach the juvenile stage in which it will start to mature and finally leave the body of the fish.
If the parasite is a female anchor worm, it will settle on the body of the fish while it still grows to turn into a worm-like shape. As the female gets large enough it will rebury itself inside the fish's skin which can cause damage and be an area in which secondary bacterial infections or fungal infections can grow from. The female will then lay its eggs on the fish's scales where they can fall off and rest at the bottom of the water. Once the water conditions are correct and the temperature is of an adequate degree, the eggs will hatch and repeat this whole process over again by either infecting a new fish or re-infected the same fish as before.
Treatment and Medication
The treatment of anchor worms can range greatly depending on much water the fish have access to, and how many fish are within the given setup. A common treatment to remove these parasites is to treat the whole tank with potassium permanganate in a ratio of 2mg per .26 gallons of water (2mg per 1 liter). Doing this will change the color of the water (so no need to panic) with an added benefit of not only killing off anchor worms that are attached to a fish, but it will also kill off any eggs that are laying on the substrate. If there are a few fish within the setup, you can always simply just remove the anchor worms using tweezers or do individual potassium permanganate solution baths in a ratio of 10mg per .26 gallons of water (10mg per 1 liter) for about 30 minutes per fish.
Due to the way that this disease affects the inhabitants, the best prevention methods are to always make sure that you quarantine anything that you place inside of your water (this includes any plants, inhabitants, decorations, and more). Thus, when you do let them adjust to your water and you truly see how they are acting, eating and if they have any symptoms or signs, we will either start to get a better understanding if they are infected or learn about what possible other diseases they might have. Note that juvenile anchor worms are microscopic, so you aren't able to see them until they mature and reach an adult stage in their lifecycle.