Koi Health and Information » Koi Diseases (Parasitic) » Gill Maggots

Gill maggots are the mature females of the parasitic crustacean Ergasilus.

Ergasilus (gill maggots) will appear as grayish black and white parasites several millimeters long infesting the gills.

Heavy infestations can cause severe damage, eroding the gill filaments and allowing secondary infections to develop.