All of my fish are attacking the same one

[CenturionElite]

Weird. One of my cory cats has been acting weird lately (swimming in vertical circles, probably a sign of vertigo) and he has been swimming erratically, basically swimming faster than usual and hyperactive.

Well recently all of the other fish seem to be picking on him. Even the other cory cats (five in total) seem to be just swarming him at different times, which is weird considering i got them all at the same time and they have been together for years. My discus recently started picking up at him and my panda garra as well. Is it possible they can sense his untimely demise?

[Wild Turkey]

Its pretty commonplace for weak/sick fish to get picked on. I would Q him immediately and closely observe him for symptoms.

[CassieLEO]

+1 Wild Turkey

Its sad, but its just what fish do...

[Lady Hobbs]

And when it dies, all the others will eat him, too.

[CenturionElite]

He died this morning :(

Is it possible the cory cats will now team up and attack each other? I have four left

[Lady Hobbs]

Never heard of that happening. A sick or injuried fish will be stalked by others because he isn't acting right so others are attracted to him. It's how the weak are eliminated.