I have had this Tang going on 2 years. It has developed a White spot on its side. This fish was quarantined for two weeks at therapeutic levels with copper power at 2.0ppm per Hanna Copper Checker. Followed by a transfer to a sterile quarantine with 2 rounds of GC. When the blue lights are on late at night, I can see some small specs of white here and there on the Tangs fins. These specs are only visible under blue lighting. The white spot in question has not changed location on the fish and can be seen under full spectrum lighting. The spot has gotten slightly larger over the last few months. I though it might be skin/flesh missing at first. Late night I have also seen the Tang Flashing and swimming erratically. Sometimes scratching on rocks. This is a tale, tale sign for me, and I know that can be an indicator for many ailments. The fish otherwise behaves normally. Eats like a pig. Normal feces. And normal respiration. I have noticed sometimes at night the respiratory rate is faster than normal. All of this being said, all of my current livestock will go through quarantine again before they are transferred to my new tank. Something could have hitch hiked in on a coral over the last couple of years as I did not quarantine all corals that went into my current system. The spot on the Tang looks slightly raised to me. I don’t think it looks like Lymphocystis. I’m really not sure what it is. All other livestock look great. Any ideas or opinions would be great!!!