What is wrong with my flame angel?

[ashleigh]

My flame is acting really strange. It is swimming very fast from top to bottom and then acts like it's having a hard time swimming straight. He then acts as if his fins won't propel him and just floats. He is not breathing hard, there are no spots. There are no visable signs of injury or illness. He just is acting panicked. At one time he was spiraling down from the top of the tank to the bottom.
90 gallon FOWLR (120 lbs)
Ammonia 0
Nitrite 0
Nitrate <10
PH 8.2
temp 78
other fish in tank
mandarin
2 small ocellaris clowns
false lemonpeel (absolutely no aggression from this fish. The flame and this fish were introduced at the same time 3 weeks ago)
cleaner shrimp
six line wrasse.
Thank you for any help or suggestions.

 

[ashleigh]

Hi Terry, it has not been netted for 3 weeks, no it has been acting normal since purchased, and yes it was QTd. He just acts panicked, probably because he isn't able to control his swimming. He got up behind the 2 overflow boxes for a while.
Thanks!

 

[ashleigh]

I just got home and the flame is dead.