Oh, yes, black spot disease, or, also called, black ick.
This disease is caused by a small flatworm that lives in the aquarium substrate. The adult worm attaches to a host fish for about six days, falls off into the substrate, then in about five days the adult body ruptures releasing a new population of young worms and the cycle begins again. It normally doesn’t show up in larger numbers as with other forms of Ich and is not nearly as dangerous. It is a disease that is fairly common with yellow tangs and angelfishes, but can effect other fish as well.
Black Spot Disease appears on the fins and body of fish as tiny black dots—about the size of pinheads. Like regular ick, the fish will scratch up against objects in the aquarium and the fish might also have reddened skin, lethargy, color loss and rapid breathing. It is easily seen on light colored fish, like the yellow tang, but is less obvious and sometimes overlooked on dark colored fish.
Some say copper treatments are not too effective and some recommend copper. Copper is a standard treatment effective for all parasites and can be applied with min. ill-effects on most fish, when used cautiously.
Using formalin treatments, trichlorofon based solutions or adding natural animal cleaners can also be a good way to treat this disease [just like it is with ICK]. Word of caution: Formalin is formaldehyde. Yes, the stuff used to embalm dead people. It is a toxic chemical and, needs to be used with care. It is, however, a common chemical used to treat incoming fish in the fish business. More likely than not, most of the fish in our tanks have already had formalin treatments/exposure before they ever made it to our tanks. It is a very toxic chemical and unless it is used properly in the correct proportions, it can result in adverse side effects and even death of the animals being treated.
When dealing with Black Ich freshwater dips can be effective. It stand to reason, then, that if FW dips work, then perhaps hyposalinity would work as well, just as it does with white ick. If so, this would be the preferred treatment. Personally, however, I am not certain on this count. Lets see if TerryB can answer that for you before proceding with these treatment options.
In the meantime, you should tell us if you set up a hospital tank or not. Unless you have a fish only tank, with no live rock, inverts, or live sand, then you will need to use a hosptal tank to treat your fish--all of them.
Also, I see that you are a new member. Welcome to Saltwaterfish.com! The forum that you posted in, however, is basically for non-hobby related communications with other members. For that reason, and because I think you will be better helped, I’m going to move your post over to our Disease Forum. See you there!