Black Ich (turbellarians)
What You Need To Know:
* Parasitic flatworm infestation; tangs are most often afflicted.
* Primary symptom is small black dots on the fish. (Not to be confused with Clownfish Hyper-Melanization.)
* Best chemical treatments for this disease are Praziquantel and Formalin. Osmotic shock (Hyposalinity, freshwater dips) is an alternative treatment option.
Additional Information
There are two species of turbellarian flatworms which are known to parasitize marine fish: Paravortex sp. and Piscinquilinus subcutaneus. Paravortex are smaller and appear as grains of black spots rather than lumps. Piscinquilinus are relatively large and lie deep within the dermis. As a result, a pigmented dermis may show once killed, resulting in a black spot, regardless of a living parasite within the skin.
Both species are thought to have a single host life cycle producing several juveniles. This cycle is completed in 10 days although from research by Justine et al. (2009) showed the Piscinquilinus remained on the fish for at least 30 days. Investigations also showed poorly developed reproductive organs indicating maturation once the parasite has left the fish. They then produce a ‘cocoon’ like fibrous structure in the substrate, within which they reproduce and therefore re-infect (Justine et al. 2008).
Treatment Options:
Cause and symptoms
Since this disease is often seen in newly acquired fish, the suspicion is that the fish bring the disease with them and become infected due to the transport stress they endure.
This parasite causes very distinctive black spots on some species of fish, most notably tangs and surgeonfish. Other fish that may become infected with Paravortex include butterflyfishes, angelfishes, gobies, and jawfishes.
The worm encysts under the fish’s skin, and the fish deposits black melanin pigment as a reaction to the infection. Since these spots are so apparent to even the casual observer, this disease is easily diagnosed, even by beginning aquarists.
Often self-limiting
The problem is that this sometimes causes the aquarist to overreact and begin a treatment that actually might be more harmful than the disease itself. It turns out that many cases of Paravortex infections are self-limiting; unless tank conditions are very poor, the worms often die out and the infection goes away on its own.
Only if the spots increase greatly in number (more than 20 spots on a fish) or the fish begin showing other signs of ill health should treatment be undertaken.
Cleanliness counts
Some aquarists have reported that careful siphon-cleaning of the aquarium substrate and improving overall cleanliness in the aquarium helps to reduce this infection. It is possible that Paravortex has a non-parasitic, free-living form at one stage of its life cycle and that careful cleaning will remove the parasite at that point.
Some turbellarians are tougher to diagnosis
There are other turbellarians that do not cause melanistic skin changes in fish and are much more difficult to diagnose. Ichthyophaga is one type known to infect fishes and can cause significant fish loss in crowded conditions. Diagnosis of this parasite generally requires a skin scrape.
It’s also noteworthy that treatment with freshwater dips may contort the worm’s body shape so much that positive identification is difficult. In some cases, no real symptoms are seen until fish loss occurs. Under the microscope, look for an oval-shaped worm with a pair of dark eyespots. There is a digenean trematode that causes similar lesions, Scaphanocephalus and related genera. These produce more diffuse black spots (often on surgeonfish) and because of their complicated life cycles, do not need to be treated as the disease won’t progress without secondary and tertiary hosts.
Treatment options
Because turbellarians cause a fairly deep-seated infection, they are difficult to remove using freshwater dips or other topical treatments. Other treatment options that have been utilized with varying degrees of effectiveness include:
A 45-minute formalin dip at 166 ppm can be effective, but then the fish must be moved to a non-infected aquarium.
Chloroquine at 15 to 20 ppm has been shown to be an effective treatment, but some fish may experience toxic reactions at this dose.
Organophosphate pesticides, such as Trichlorfon (Dylox), have been the treatment of choice for many years but cannot be recommended due to their potential toxicity to humans.
Some treatments are not effective, but because this disease is often self-limiting, they can appear to work:
Praziquantel at 2 mg/l is a safe, commonly used treatment for trematode worms, but despite being “prescribed” by many people, it is not effective for turbellarians. Praziquantel doesn’t kill worms, it just causes them to relax their grip and let go of the fish. These turbellarians are beneath the skin, so do not drop off easily when exposed to praziquantel.
Copper treatments are ineffective, at least at the concentrations well tolerated by fish.
What You Need To Know:
* Parasitic flatworm infestation; tangs are most often afflicted.
* Primary symptom is small black dots on the fish. (Not to be confused with Clownfish Hyper-Melanization.)
* Best chemical treatments for this disease are Praziquantel and Formalin. Osmotic shock (Hyposalinity, freshwater dips) is an alternative treatment option.
Additional Information
There are two species of turbellarian flatworms which are known to parasitize marine fish: Paravortex sp. and Piscinquilinus subcutaneus. Paravortex are smaller and appear as grains of black spots rather than lumps. Piscinquilinus are relatively large and lie deep within the dermis. As a result, a pigmented dermis may show once killed, resulting in a black spot, regardless of a living parasite within the skin.
Both species are thought to have a single host life cycle producing several juveniles. This cycle is completed in 10 days although from research by Justine et al. (2009) showed the Piscinquilinus remained on the fish for at least 30 days. Investigations also showed poorly developed reproductive organs indicating maturation once the parasite has left the fish. They then produce a ‘cocoon’ like fibrous structure in the substrate, within which they reproduce and therefore re-infect (Justine et al. 2008).
Treatment Options:
- Praziquantel – 2 mg/L single dose for 7 days in a QT. Both Prazipro (2.5 mg/L) and API General Cure (2.0 mg/L) contain sufficient concentrations of praziquantel. (see below)
- Formalin – 45 to 60 minute bath treatment, followed by transfer into a sterile QT afterwards.
- Hyposalinity – Treat at 1.009 SG for at least 10 days. This kills both the infective and free living stages of the life cycle.
- Freshwater Dip – 5 minute freshwater dip may only provide temporary relief, and not result in complete eradication.
Turbellarian Infection (a.k.a. black spot disease, black ich, tang disease)
Turbellarians are a group of worms related to trematodes. They often go undiagnosed as a cause of active infections in fishes except for one group: Paravortex sp.Cause and symptoms
Since this disease is often seen in newly acquired fish, the suspicion is that the fish bring the disease with them and become infected due to the transport stress they endure.
This parasite causes very distinctive black spots on some species of fish, most notably tangs and surgeonfish. Other fish that may become infected with Paravortex include butterflyfishes, angelfishes, gobies, and jawfishes.
The worm encysts under the fish’s skin, and the fish deposits black melanin pigment as a reaction to the infection. Since these spots are so apparent to even the casual observer, this disease is easily diagnosed, even by beginning aquarists.
Often self-limiting
The problem is that this sometimes causes the aquarist to overreact and begin a treatment that actually might be more harmful than the disease itself. It turns out that many cases of Paravortex infections are self-limiting; unless tank conditions are very poor, the worms often die out and the infection goes away on its own.
Only if the spots increase greatly in number (more than 20 spots on a fish) or the fish begin showing other signs of ill health should treatment be undertaken.
Cleanliness counts
Some aquarists have reported that careful siphon-cleaning of the aquarium substrate and improving overall cleanliness in the aquarium helps to reduce this infection. It is possible that Paravortex has a non-parasitic, free-living form at one stage of its life cycle and that careful cleaning will remove the parasite at that point.
Some turbellarians are tougher to diagnosis
There are other turbellarians that do not cause melanistic skin changes in fish and are much more difficult to diagnose. Ichthyophaga is one type known to infect fishes and can cause significant fish loss in crowded conditions. Diagnosis of this parasite generally requires a skin scrape.
It’s also noteworthy that treatment with freshwater dips may contort the worm’s body shape so much that positive identification is difficult. In some cases, no real symptoms are seen until fish loss occurs. Under the microscope, look for an oval-shaped worm with a pair of dark eyespots. There is a digenean trematode that causes similar lesions, Scaphanocephalus and related genera. These produce more diffuse black spots (often on surgeonfish) and because of their complicated life cycles, do not need to be treated as the disease won’t progress without secondary and tertiary hosts.
Treatment options
Because turbellarians cause a fairly deep-seated infection, they are difficult to remove using freshwater dips or other topical treatments. Other treatment options that have been utilized with varying degrees of effectiveness include:
A 45-minute formalin dip at 166 ppm can be effective, but then the fish must be moved to a non-infected aquarium.
Chloroquine at 15 to 20 ppm has been shown to be an effective treatment, but some fish may experience toxic reactions at this dose.
Organophosphate pesticides, such as Trichlorfon (Dylox), have been the treatment of choice for many years but cannot be recommended due to their potential toxicity to humans.
Some treatments are not effective, but because this disease is often self-limiting, they can appear to work:
Praziquantel at 2 mg/l is a safe, commonly used treatment for trematode worms, but despite being “prescribed” by many people, it is not effective for turbellarians. Praziquantel doesn’t kill worms, it just causes them to relax their grip and let go of the fish. These turbellarians are beneath the skin, so do not drop off easily when exposed to praziquantel.
Copper treatments are ineffective, at least at the concentrations well tolerated by fish.
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what about this prazi thing they're talking about? 
