HLLE is common in Tangs and Angels. I just lost my Yellow Tang to the disease. It comes from nutrient deficiencies, stray voltage in you're tank, and the protozoan Octamita ( Hexamita ) necatrix. I tried every cure in the book that I have on saltwater aquariums. The book is " The Conscientious Marine Aquarist " by Robert M. Fenner. But all the efforts that I tried failed and my tang died today. Just a little heads up for everyone that has tangs or angels. The disease will start with the fishes pores starting to enlarge, then the scales on their head and lateral line will start to disappear. Causeing eventual death.