Blue tang is hurting himself

[Jpino004]

i have a small blue tang that i bought a few weeks ago. i previously had a brown tang in the tank also but removed it becuase they would try to fight. but i have been noticing is that my blue tang scratches his side against the sand.

when i woke up today one of his sides has a big grey mark. (i suppose he took off some scales)

anyone have an idea why it does this, what it might be and how can i stop it?

thanks

[Gwynhidwy]

What type of 'blue tang'? Paracanthurus hepatus? Acanthurus leucosternon? Acanthurus coeruleus?

If it is a Paracanthurus hepatus, the scrape on his side could be from wedging himself in the rocks at night as they like to do that and often cause scarring from doing so.

The scratching on the sand behavior, often called flashing, could be indicative of parasites like flukes or ich. Did you quarantine this fish? If so, for how long and did you treat the fish with anything during that time?

[Jpino004]

yes it is a Paracanthurus hepatus. im yet to quaratine the fish. he does both of those things. he does the flashing and the wedging between the rocks. how do i treat the fish for parasites? im somewhat new to this

[Jpino004]

i went to the local fish store and they told me to take out the carbon from the filter, and gave me a medicine to put int he water. im going to buy a cleaner shrimp tomorrow to see if he picks the parasite off of the tang.