Most Common Tang Ailments and Treatment Protocols
Tang Husbandry

You will hear some people refer to many tangs as “ich-magnets.” Now we don’t like this one bit because first, marine fishes don’t get “ich”, and second, in our experience, if a tang is fed a nutritious and varied diet and is kept in an aquarium with stable, high quality water with a salinity close to natural seawater, the fish is not overly susceptible to protozoan parasites like Cryptocaryon and Amyloodinium. In this article, we are going to emphasize the importance of good husbandry when keeping tangs—an ounce of prevention is worth a pound of cure. We will also, however, look at some of the common ailments are the most effective treatment protocols for those ailments.

Good Husbandry is the First Line of Defense

Tangs are not, in our experience, overly susceptible to parasites and other ailments when they are kept properly. By properly, we mean a stress free environment where a varied and nutritious diet is readily available. The average tang tank should be large (really nothing under 75 gallons and much, much larger for some species) and have plenty of live rock AND plenty of swimming space. Water movement should be brisk, as this assists with oxygen exchange at the surface. Tankmates should be appropriately chosen so as not to cause undue territorial aggression.

Nutrition is critical for tang health. Be sure to offer quality foods prepared for herbivores, and offer dried marine algae regularly in the form of sheet food like nori or an aquarium-specific product like Sea Veggies. Macroalgae grown in a refugium is fantastic foodstuff for many tangs. As mentioned above, the tank should have plenty of live rock, and it should not be “too tidy” in terms of filamentous algae. In the wild, tangs spend the day picking at the reef in search of their favorite food, and they will want to do the same in your aquarium.

Most tangs will readily accept just about any prepared food you offer to your other fishes. Use this fact to your advantage, and feed flake food that has been soaked in a vitamin supplement like Selcon to your tang. This will assist with the fish’s immune system and will insure optimum nutrition.

Crypto and Other Infestations

If you do notice that your tang, despite your best efforts, is showing signs of infestation or any other ailment, you are advised to respond quickly. One of the more common ailments of which you hear people speaking in relation to tangs is cryptocaryonosis, sometimes simply called "crypto." This is a disease caused by the parasite Cryptocaryon irritans which bores into the fish’s skin and gills. The parasite is then covered with mucus produced by the fish as part of the fish s natural defense mechanism. It is this mucus buildup that the aquarist is referring to when he or she says, "My fish has white-spot disease." You may also see the spots on the eyes of the fish or on the fins or tail. In addition, the parasites bore into the gill structure, causing respiratory difficulty for the fish.

If you observe these white spots, quickly remove the fish to a quarantine tank for treatment. If you observe the white spots on all of your fish, you will need to remove them all from your aquarium for a period of about one month. Leaving the tank fallow for this length of time, should break the life cycle of the parasite and prevent future outbreaks once your fishes are returned to the tank.

·        Treatment of the affected fish usually involves some or all of the following procedures:

·        Freshwater dips dosed with methylene blue plus formalin

·        Lowering specific gravity (hyposalinity = 1.010-1.013) of the quarantine tank

·        Continuous exposure for at least 28 days to 0.15 to 0.20 ppm copper, although copper in and of itself can have long-term negative effects

·        Antibiotic feeding (preventative against secondary infection)

There are several other protozoan infestations of which the marine aquarist should be aware. They are Amyloodinium ocellatum (sometimes called marine velvet disease) and two additional ciliate protozoans, Brooklynella hostiles (sometimes called anemonefish disease) and Uronema marinum (often called uronema). All three of these can affect tangs, and all can be devastating to your system if not treated quickly. All three infestations present in roughly the same way (skin damage, rapid breathing, rubbing on rocks and substrate, and extreme lethargy) and are the results of very similar parasitic organisms with almost identical life cycles. All are commonly treated with the same procedures.

Hole-in-the-Head Disease

Hole-in-the-head disease is commonly associated with tangs (and angelfishes), but relatively little is known about what it is, what causes it and how to effectively treat it. The information presented here is mostly anecdotal, but here it is.

Hole-in-the-head disease is believed to be caused by a flagellated parasite that occurs commonly in the gastrointestinal tracts of health marine fishes. When populations of this parasite grow too large, infested fishes will lose their coloration and their appetite. They will act abnormal (e.g., a tang sulking in a dark corner of the tank) and their fecal matter may become white and slimy in appearance. Pitting of the flesh on the fish’s head is also sometimes observed (hence the name), but the overgrowth of these parasites usually occurs in the intestinal tract.

If you suspect hole-in-the-head disease, it is recommended to remove the fish to a quarantine tank where it can be nursed back to health. In the quarantine tank, metronidazole can be added to the water at a concentration recommended by the drug manufacturer. Seachem makes a widely available product containing metronidazole called AquaZole. There are other options including the human drug Flagyl.

Some aquarist also recommend soaking foods in metronidazole if the fish is still feeding and then feeding the medicated foods. Unfortunately this is often difficult as a fish suffering from hole-in-the-head disease will not be eating.

Head and Lateral Line Erosion (HLLE)

The condition referred to as head and lateral line erosion (HLLE) is different from the above ailments as it is a non-pathogenic ailment. A tang afflicted with HLLE will present with pitting and scarring along its lateral line and on the head. Fading color is also quite common. Like hole-in-the-head disease, HLLE is not very well understood, but it is our experience that it is often related to malnutrition or prolonged exposure to hyposaline conditions. Stray electric current (e.g., from faulty powerheads) is also sometimes believed to be the culprit.

There are many other suspected causes of HLLE, and because the causes are not well understood, effective treatment can be difficult to nail down. Here is what we suggest:

·        Insure water quality is high and stable

·        Use a supplement for synthetic saltwater such as Kent Marine’s Essential Elements

·        Insure a varied and nutritious diet (using a vitamin supplement like Selcon) is being offered

·        Reduce the amount of chemical filtration (if any) on the system, especially activated carbon

·        Remove any potentially faulty powerheads, heaters or other equipment that could be releasing stray voltage into the aquarium

Frequently HLLE will not lead to death, but rather it will result in disfiguration and, ultimately, discomfort to the animal necessitating euthanasia. If you observe the signs and symptoms, act quickly.