My tangs use to get white spot/ich from time to time and i left them to their own to cure, the help i had in the tank were some cleaner shrimp, and gobies. of course if you have corals the shrimp may be risky. at any rate if white spot is what you have, then the following bath will help for each infected fish (Chloramin T / long bath/ 10 mg/l / use with care. Most poprietary treatments will deal with white spot, vevet, protozoan parasites and monogenetic trematoldes. In the US, organophosphates such as trichlorofon, which treat crustacean and Black Spot parasites, are available in proprietary form. Look for products containing the following active ingredients: Quinine, Copper, Acriflavine, Formaldehyde, Methylene Blue, and Malachite Green.
The problem with paracites is that a secondary bacterial infection can start. here is some information that may be helpful;
* Long Bath - with this method the water soluble treatment is added directly to the water of your extablished aquarium. the dose is carfully formulated so that it is not toxic to the fish for the full duration of the treatment but effective against the pathogen long bath treatments have the advantage of being simple to administer and eradicating the disease pathogens both on and off the fish/ I recommend a quarintine tank as the medication will also kill your good bacteria and if you have a community / mixed tank with corals/inverts you will need to isolate the affected fish and treat individually.
FINALLY: Fish parasitism is an association where the parasite is dependent on and derives benefit from the host fish who derives no benetit. Parasites come in a large number of forms, viruses, protazoa, crustaceans, roundworms, flukes, tapeworms and trematodes. the associateion between parasite and fish host can take many forms. white spot for example spend only part of their life cycle on their host fish. Most fish and invertebrates are disease carriers. They contain parasites that their immune system has not completely eradicated, but that have been kept sufficiently in check so that there is no evident sign of disease. The marine aquarium environment also contains a number of pathogenic bacteria and fungi, but again a healthy fish's immune system ensures that these do not cause disease. In the aquarium there exists a delicate balance between the fish and the disease organisms present. anything that upsets this balance will lead to a disease outbreak. The first line of defense from parasites invading the fishes body is an effective outer barrier in the form of scales, and the layers of the dermis and epidermis of the skin, all of which provide some protection against disease organisms and physical damage. The outer barrier is further improved by a covering of mucus that conatains a number of bactericides and fugicides. the mucus membrane is constantly being renewed, which also has the effect of sloughing off debris and dissuading the proliferation of external parasites. the other possible area of infiltration is through the digestive tract, where enzyme action and an unsuitable ph produce a hostile environment which discourages most pathogens. If one of these barriers breaks down then pahtogens can gain entry, through skin wounlds, and through the gut. So if you have a light case of white spot if that is what it is, i would recommend working on the fishes immune system and slime coat to help the fish fight off the parasite naturally, add several cleaner gobies, keep an eye on the rest of the fish. You did not say if you had a a mixed coral/fish aquarium. at any rate hope something here helps. a drop in temperature as quickly as you did probably saved your charges, but, also created the stress needed to start an out break. keep up the garlic, add several gobie cleaners and let us know how you progress. keep an eye on your water parameters, salinity, ph, hardness, etc. with a large drop in temperature you will need to watch your system closely for a few weeks. hope something here helps. good luck. OH!! and WELCOME TO THE FORUM.
