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Black Spot or Tang Disease

Black Ich Diagnosis and Treatment


What is Black Spot Disease?

Typically a "disease" that is most commonly associated with Tangs and Surgeonfishes, but one that can be contracted by other species as well, what is referred to as Black Spot Disease, Tang Disease or Black Ich is actually caused by an infestation of tiny Genus Paravortex member turbellarian flatworms.

Although parasitic organisms that are much less dangerous and life-threatening, as well as rather easy to get rid of compared to other ich diseases such as Oodinium, Cryptocaryon, and Brooklynella, nonetheless it is a problem that needs to be treated upon recognition to eradicate infected fishes of these parasites.

The Life Cycle of These Worms

  • Living in the substrate until mature, an adult worm seeks out a host fish.
  • After feeding for about six days, it falls off into the substrate.
  • About five days later the worm's body ruptures and releases a new population of young worms, and the cycle starts again, but in larger numbers.

Symptoms to Look For

Once these worms start feeding on a host fish they acquire pigmentation, which causes the appearance of black spots about the size of a grain of salt on the body and fin membranes. Worms that freely move about on fish, the spots do not always remain stationary. On light colored fish they are easy to see, whereas on dark colored ones they may go unnoticed at first. Fish will scratch up against objects in an attempt to dislodge the parasites, and if allowed to progress the fish become lethargic, loss of appetite and colors occur, rapid respiration develops, and secondary bacterial infections can invade damaged tissue sites.

Treatment Recommendation

Give all infected fish a freshwater dip, followed by a formalin bath and continue treatment in a QT.

Preventing Reinfestation

Reinfection will occur no matter how effectively the fish have been treated if these parasitic tubellarian worms are not eradicated from the main aquarium. Unfortunately because they can survive for several months without a host, this is often not an easy thing to do, but here are some suggestions.

  • Leave the main aquarium devoid of all fish for several months.
  • Young worms live in the substrate and feed on detritus and organic debris until such time they mature and go in search of a fish host. By siphoning up excess organic matter that can build up on the bottom of the aquarium can help to control their numbers.
  • For fish-only tanks that have no freshwater sensitive invertebrates present, hyposalinity can be applied.

~ Debbie & Stan Hauter

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