Just tried to get another picture before the lights went on, spots kind of look dark today. His fins are also clear some one mentioned the saw spots on his fins in one of the other pictures but I never saw his fins with spots yet. Still ich you think
While black spots on a yellow tang are almost always "black ich", a turbellarian worm, the original photos that you posted are NOT that disease. So - why the black spots now? Tough to say. It could be that the fish is producing melanin as a reaction to the original ich infection, or it could also have both diseases at the same time.
Here is some text that I wrote about the tang turbellarian:
Turbellarian
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 a type known to infect fishes and can cause significant fish loss in crowded conditions. Diagnosis of this parasite generally requires a skin scrape.
Treatment options
Because turbellarians cause a fairly deep-seated infection, they are difficult to remove using topical treatments. Other treatment options that have been utilized with varying degrees of effectiveness include:
Praziquantel at 2.2 mg/l is a safe, commonly used treatment for trematode worms, but despite being “prescribed” by many people, it is not very 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.
A freshwater dip. for five to seven minutes, followed by moving the affected fish to a non-infected tank is moderately effective at treating encysted turbellarians. The process may need to be repeated a total of three times, every five days.
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.
Copper treatments are ineffective, at least at the concentrations well tolerated by fish.
