There are three parasites that affect goldfish and koi that you can see without the aid of a microscope. They are Ich, Fish Lice, and Anchor worm. Today we take a look at Anchor Worms.
What is it?
Lernea, better known as Anchor Worms, resemble brown or greenish threads on the body, fins,or tail of goldfish and koi. About 1/8 to 1/4 inch in length, these parasites, unlike most that affect your fish, don't rely on fishes' immune suppression to attack. If they're present in your system or pond, they will proliferate.
What to do?
These guys typically don't kill fish, as some of the microscopic parasites do, but they will cause damage by punching holes in your fish which can lead to ulcer disease. So they will need to be eradicated. For individual fish you can remove the worms with tweezers and disinfect the puncture wound with Iodine or Mercurochrome. But that's not the end of the story. Now you need to deal with the "un-attached" life stage and eggs that are still in your pond or system. Medications containing Dimilin used to be the treatment of choice. Unfortunately, those products are no longer available commercially. Look for medications containing Trichlorafon or Cyromazine. The ones I'm familiar with are:
• Cyropro by Pond Solutions
• Paracid by Crystal Clear
• Lice and Anchor Worm by Microbe Lift
• Proform LA by Koi Care Kennel
Keep in mind that you MUST re-dose according to the label as you are killing off the Lernea's vulnerable nauplii life stage as it cycles from egg to adult.