I have seen the phenomnon. Everybody in the tank seems fine but the Powder Blue/Brown or Hippo gets it. They get it on and off. It seems to come and go, but never leaves, leaving you scratching your head.
I have a thought.
Background. I have the butterfly version of the Powder Blue/Brown tang. That would be a Pakastani Butterfly. When he arrived he had two small white spots. I don't worry too much about this because my tank is set up with high flow and surface skimming to encourage good oxygen content. I also have have good biodiversity through live rock. These are my base preventatives for dealing with ich. I also recieved a Sunset Butterfly the same time as the Pakastani and she did a little head shaking but that was about it. The ich on the Pakastani got worse. The Sunset got better. The Pakastani got more spots on his tail and lower dorsals and he was pacing and head shaking constantly. He quickly started eating the white worms that I fed so I didn't worry.
Now to my thought. I noticed that there was a TON of light pollution in my tank. I have decent amount of hiding places in the rock for the fish but the Pakastani would sleep out in the open. Essentially he would be awake the entire night. He would never sleep. Sometime back I had a maintenance tank in a hospital and had 3 Pakastanis in it. They all died because the light in the room that they were in never went out. It occured to me that this stressor of not sleeping was keeping the ich coming back. With that thought in mind my wife started to cover the tank with sheets at night. This seemed to do the trick the ich started to abate and the fish started to calm down.
Aftermath. The Pakastani has stopped pacing and the spots are all gone. The fish seems calmer. He still has the head shakes occasionally but I am sure that that will go too.
Just a thought for people that are having problems with chronic ich on their tangs.
I have a thought.
Background. I have the butterfly version of the Powder Blue/Brown tang. That would be a Pakastani Butterfly. When he arrived he had two small white spots. I don't worry too much about this because my tank is set up with high flow and surface skimming to encourage good oxygen content. I also have have good biodiversity through live rock. These are my base preventatives for dealing with ich. I also recieved a Sunset Butterfly the same time as the Pakastani and she did a little head shaking but that was about it. The ich on the Pakastani got worse. The Sunset got better. The Pakastani got more spots on his tail and lower dorsals and he was pacing and head shaking constantly. He quickly started eating the white worms that I fed so I didn't worry.
Now to my thought. I noticed that there was a TON of light pollution in my tank. I have decent amount of hiding places in the rock for the fish but the Pakastani would sleep out in the open. Essentially he would be awake the entire night. He would never sleep. Sometime back I had a maintenance tank in a hospital and had 3 Pakastanis in it. They all died because the light in the room that they were in never went out. It occured to me that this stressor of not sleeping was keeping the ich coming back. With that thought in mind my wife started to cover the tank with sheets at night. This seemed to do the trick the ich started to abate and the fish started to calm down.
Aftermath. The Pakastani has stopped pacing and the spots are all gone. The fish seems calmer. He still has the head shakes occasionally but I am sure that that will go too.
Just a thought for people that are having problems with chronic ich on their tangs.