About two weeks ago, I noticed several tiny white spots on my adult powder blue tang and treated for Ich with a bottled med and a freshwater dip. The next day it was much worse. It cleared up the next day after a second treatment. He behaved normally and ate healthily. Three days ago, he started breathing rapidly, formed white flakes on his skin, his fins turned reddish orange, and swam at an angle. My neighbor, who moved yesterday and no longer available, looked at him and suggested hemorrhagic septicemia. I went to Petsmart for a broad spectrum antibiotic and it seemed to help during the day cycle. Some of his color returned yesterday, his fins looked healthy, and my hopes were raised. Today, however, he spent most of the day on his side in the back corner near the heater and is not eating. He will swim momentarily as if looking for food but then sinks to the bottom and lays on his side. I have two other fish in my 20 gallon tank-- a clown and a blennie, both of which are fine. I had the tang for about six weeks or so and it was doing wonderfully until the other day. My water levels are fine. I changed the filters, did a 50% water change, and added an additional chemical filter. My system is set up to handle 75 gallons as I plan to upgrade after gaining experience. I use only RO/DI water. I purchased another turbo snail and 10 hermit crabs just before the tang got sick and thought perhaps the inverts brought Ich to the tank. They are all alive and well. At this point, can my powder blue recover or would euthanasia be more humane? I hate to see him suffer. I've had the tank about six months and this is my first brush with disease.