Yellow Tang attacking glass constantly

[Ridgeback1]

I have a Biota Yellow Tang that has been doing great since I got it 8 months ago--it has grown to about 5 inches and is robust, deep yellow, eats well, is peaceful to other fish, and until recently cruised about the tank happily nipping at rock for algae. Tank is 7 feet and 327 gallons with plenty of live rock and also negative space for swimming. About a month ago a gyre pump (now removed) had a snail get caught and it made a massive grinding noise. I can't say for sure that was the trigger, but at that point the tang stopped swimming around and spent all his time rushing at and charging a lower corner of the front glass (the same corner below where the offending gyre was, but I can't say that was more than coincidental). I blocked the corner so he can't see out of it and that seemed to solve it--he went back to swimming the tank for a few days--but then he simply moved laterally down the tank to where it isn't blocked out and resumed his charging behavior. When the lights go down he stops the behavior and he will stop to eat when food is presented. This has been going, as I noted, for a month and he is relentless. Any ideas?

 

[mcarroll]

Sounds like HE WANTS OUT!!!!

I would try the mirror trick down on that end of the tank....or maybe a complete tank rearrange.....or trade him to another tank.