| Hi there
Here is something you can look at:
What is it?
Black Spot is actually the larvae of a parasite. It is often brought into the aquarium by new fish or snails. The parasite has a quite complex lifecycle- and would be very lucky indeed to actually complete it! It starts out (if a life cycle can start…) with snails. Eggs of the parasite in the water of creeks or rivers hatch and infect snails. Inside the liver of the snail they slowly develop, until eventually leaving the snail to find a fish. When they find a fish the larvae burrow under a scale in the fishes skin (causing much irritation to the fish). The parasites then hope the fish will be eaten by a bird or other animal so that the lifecycle can continue. When they are eaten they quickly mature in the intestines of the host animal and produce large numbers of eggs. These eggs are then excreted, making their way back to the water of a creek or river. And the cycle continues!
However, if a fish in an aquarium is infected, the parasites are out of luck! Their lifecycle comes to an abrupt stop as there are no birds or animals to eat them.
More good news, Black Spot will rarely kill fish (that is not in their interest, they want the fish to live… then be eaten!) It does cause irritation and some stress however, so it is best to try to get rid of them. Occasionally if the parasites concentrate on the eyes, the fish may go blind.
Symptoms:
The most obvious sign is the small black spots, measuring approx. 2mm in diameter (.08 in). Fish may also exhibit behavioral signs, such as scratching against aquarium objects and flicking of their fins.
Cure:
Black Spot is fairly easy to cure. First and foremost, remove all snails from the aquarium. And that's about it! The parasites can not mature further so eventually die. If any of the sites of attachment get infected by bacteria, use a mild antibiotic available from your local aquarium store. This rarely happens however, so is not usually necessary.
Remember, water quality is always extremely important- so always check that first as it is often the cause of disease in aquarium fish. When treating sick fish, try to put the least amount of stress on them as possible, as stress will hinder the heeling process. Another thing is to remember is that generally, a healthy fish is a happy fish.
If this is not quite what you're looking for you can google some more. | 
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