Hi Dj,
Not sure if this is what you got but, anyway is it BROWN or BLACK color? if brown, grey or white probably a Fungus(use Methylene blue) if Black:Black Spot DISEASE Caused by the larval stage of digenetic fluke parasites, such as Clinostomum, Posthodiplostomum and Dipplostomum.
SYMPTOMS Black color cysts develop on the body and fins. Small numbers cal do little harm but large numbers can harm small fish.
TREATMENT Very rarely necessary and is difficult if not impossible.
PREVENTION Avoid obviously infected fish and discourage fish-eating birds from visiting garden ponds to prevent the life cycle being completed.
Joe
www.cichlidfish.com