Need a bit more details about what you see, what's going on, etc.
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Sorry about that.
Tang eats fine and swims fine. He has a light pink color under the eye and under side of fish.
Nitrate is 40 everything else is good. I have tryed to get the nitrate down by doing water changes.
tank has been running for about 4 months now.
Paul
Paul, tangs have little tolerance for nitrate. You might need to find another home for this fish.
Take a look at the tangs in the Diseased Fish Thread at the top of this forum that have HLLE [Head and Lateral Line Erosion].