Fox Face black/brown spots

[Ranger11]

Hello, My name is Frank. I have a 165 gallon salt water tank. Live stock dog face puffer,coral beauty emperor angel and fox face . Today, I found my fox face dead, but before this I did notice that my emperor was chasing him around and nipping at him. Fox face was the aggressor of all the fish before this. The fish that I mentioned earlier have been in tank together for over a year . My question is was the black,brown spots caused by emperor or was it something else? Thanks

 

[lmforbis]

The spots were probably stress spots. They get s a spotted coloration when they are stressed so they can blend in to their surroundings. The stress was probably caused by the Angel.

 

[Ranger11]

Thank you for responding. I don't understand why they fought they were in tank for over a year with no problems.

 

[lmforbis]

As fish reach maturity, like most animals, they become more territorial and as a result more aggressive to tank mates. Mature Angels are known to be aggressive.