First some history. In March of this year my first two fishes were a clown and a diamond goby. After a goby suicide, I replaced him. a couple of months later I added a white firefish. Then a few weeks later I added a purple firefish, another clown and a royal dottyback. A month or two have past since then.

 

THe other night my goby was normal. Eating and digging and sifting. Then that very night I witnessed the dottyback harassing the goby. The next day his nose was red and cut up a little and his tail was shredded, little movement, no eating. Over the next three days his condition worsened until his death today.

 

What caused the sudden aggresiveness out of the dottyback? Will a sick fish get picked on? I know getting picked on will make them sick. All other fish seem relaxed and happy.

 

Any thoughts??

 

Thanks!