Orange shoulder tang acting funny

[mattjd]

So I’ve had this orange shoulder tang I n my 75 gallon FOWLR tank for about 24 hours. both last night and this afternoon I noticed that every once in a while he will go lay with his mouth to the corner of the glass and substrate and move forward quickly, at first glance it looks like he’s eating algae buildup but as he goes forward he will start rubbing his dorsal fin along the glass and mouth on the substrate while completely sideways. Also, throughout the entire time that the fish is doing this he will progressively change color from yellow to black and when he stops laying he starts swimming normally and will immediately change back to a bright yellow color.
Video posted below
As I said he’s new in the tank, he was added at the same time as a very timid fire fish and there were already three blue damsels in there some first day aggression but they all seem calm with each other now. Both new fish have eaten twice since being put in the tank and seem to be healthily picking at algae.

Can anyone identify and explain the tangs behavior and color changing and let me know if it’s something to be worried about

 

[mattjd]

These are stills from the video I couldn’t get to post correctly
The picture where he is vibrant yellow is about 10 seconds after the one where he is all black except for his tail fin

 

[Cheese Griller]

It looks like he could be squaring off against his reflection, which would explain the color change.

 

[mattjd]

It looks like he could be squaring off against his reflection, which would explain the color change.

That’s an interesting thought, he’s still doing it every once in a while but he only does it in that one spot in the tank specifically he goes over to the timid fire fish, who hasn’t left that corner since he was added to tank except to hide in rock work to sleep, stares at him and then turns black and does that odd movement.

He doesn’t seem to be hurting the fire fish, he seems to be trying to entice him out of the corner.
I’m not really concerned about Illness at this point because it seems like he has control of this action based on him doing it in the same spot in the tank every time.

 

[Cheese Griller]

That’s an interesting thought, he’s still doing it every once in a while but he only does it in that one spot in the tank specifically he goes over to the timid fire fish, who hasn’t left that corner since he was added to tank except to hide in rock work to sleep, stares at him and then turns black and does that odd movement.

He doesn’t seem to be hurting the fire fish, he seems to be trying to entice him out of the corner.
I’m not really concerned about Illness at this point because it seems like he has control of this action based on him doing it in the same spot in the tank every time.

yeah color changing like that is generally in reaction to another fish (or reflection) in my experience. Very cool to see how quickly he can do it! From the video it looks like he has good control of his swimming and whatnot so I would just monitor to make sure that doesn't change.

Slightly off-topic but that orange shoulder is going to outgrow the 75 eventually, I'm not positive on their growth rate but I've seen them top out over a foot long!