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Tropical Fish Parasites, How to Identify

Drs. Foster & Smith Educational Staff
Manage Water Temperature 
Water Temperature & Ich Prevention 
Saltwater Ich (Cryptocaryon irritans
Fish Health & Nutrition
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How to Identify Common Tropical Fish Parasites
The best prevention against parasites is to keep your fish healthy in a stress-free environment. Healthy fish rarely get sick even if exposed to infected fish unknowingly introduced into the aquarium. Proper aquarium setup and water parameters, routine maintenance, quality nutrition, and minimizing aggression among inhabitants are easy ways to improve fish health and reduce infection.

Common aquarium parasites
Despite our best efforts, most aquarists will need to deal with parasitic infection. The most common parasite in both fresh and saltwater aquariums is "Ich" or white spot disease. Other common fish parasites include anchor worms, black spot, costia, gill flukes, hexamita, fish lice, and velvet. All can pose a serious threat to the health of your fish. Because of their size, the presence of parasites is often diagnosed initially through abnormal fish behavior. Once the parasites are well established, physical damage can be observed on the infected fish.

Parasite Symptoms and Treatments
If you observe the behaviors described below, you may need to take corrective action*:

Disease Signs Recommended Treatment*
Anchor Worm
Anchor Worm: Photo courtesy TFH Publications
Whitish red worm-like threads approximately 1/4" in length, found anywhere on the body, fish may scratch on fixed objects Treat with an anti-parasitic medication; or treat aquarium with PimaFix to quickly clear external and internal parasites from tropical fish
Costia: Photo courtesy TFH Publications
Grayish-white film or excess mucous over entire body; reddening under the mouth and pectoral area; scratching on fixed objects; listlessness Use Malachite Green, treat all fish and aquarium
Gill Flukes
Gill Flukes: Photo courtesy TFH Publications
Gills become covered with parasites, red and inflamed; fish may gasp for air at surface; listlessness Use ParaGuard
Freshwater: Ich (Ichthyophthirius multifiliis)
Marine: Ich (Cryptocaryon irritans)
Ich: Photo courtesy TFH Publications
Labored breathing; dwelling near the surface, filters, or aeration devices; white spots; scratching on fixed objects Freshwater and Scaleless: Use Rid-Ich+ or Ich-Attack
Marine**: Use Cupramine as recommended. Use Garlic Xtreme as a preventive.
Hexamita (Hole-in-the-Head)
Hexamita (Hole-in-the-Head): Photo courtesy TFH Publications
Small holes may appear over the entire body, but most frequently on the head; mucous string from lesions; loss of appetite; faded color Use Parasite Guard or Metro+ Hole-in-head/Lateral Line Treatment; also feed a high quality food and vitamins
Fish Lice
Fish Lice: Photo courtesy TFH Publications
Visible parasite attached to fish, approximately 3/16" long and semi-transparent Use Cupramine
Freshwater: Velvet
Marine: Amyloodinium ocellatum
Velvet: Photo courtesy TFH Publications
Loss of normal color, scratching against fixed objects, labored breathing, golden "velvety" growth on skin Freshwater: Use Parasite Clear
Marine**: Use Probiotic Marine Formula or Cupramine

*Please note: Activated carbon will remove all medications from the aquarium. When using medication, activated carbon must be removed from the filtration unit.

- Perform a 25% water change before and after treatment period.

- In addition to treatment, be sure to determine and correct aquarium conditions that contributed to fish stress and susceptibility to disease.

**We recommend that treatment of marine fish be done in a separate quarantine aquarium.

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