Worms Hanging from Koi: Parasite Emergency, Not Eggs

"Worm-like things" coming from a "pregnant" koi. Eggs or parasites?

Koi Don't Get "Pregnant"

They spawn (release eggs). A swollen female is gravid (egg-filled), not pregnant. Worms protruding from the vent/body are parasites. Anchor worm (Lernaea), leeches, or internal nematodes exiting.

Immediate Steps

1. Net & Examine: Close look. Anchor worm = Y-shaped anchor under scale. Leech = segmented, suckers. Nematode = thin, threadlike.
2. Isolate: Hospital tank with pond water, air stone.
3. Identify & Treat:
   • Anchor worm: Tweezer removal + potassium permanganate dip or Dimilin (diflubenzuron) pond treatment.
   • Leeches: Salt (0.3%) + manual removal.
   • Internal worms: Medicated food (levamisole, praziquantel).
4. Treat Pond: Based on ID. Dimilin covers anchor worm/leeches. Safe for plants at label rate.

Don't Guess—Magnify

Phone macro photo → Google Images "koi anchor worm," "koi leech," "koi nematode." Match it. Treat correctly.

Other fish are at risk. Act fast.