Fish twitching

[WilliamG]

My Shark fish, Balantiocheilos melanopterus, has started to twitch. He seems to be trying to get through the glass at the end of the tank. But what troubles me the most is that he never seems to stop twitching. Any help would be appreciated.

 

[GaryE]

They're famous long distance, high speed swimmers, and a fish many consider unsuited for aquarium life as a result. Are there any signs he might have crashed into the glass and done himself a neurological injury? Injuries around the face or snout?

 

[WilliamG]

No, he just will not stop moving his body in swimming mode. He swims away from the end but keeps moving his body back and forth even when he swims. He has been with me about 6 months now. This is new behavior.

 

[GaryE]

Often 'shimmying" in fish is neurological in origin. If it is, there's nothing you can do. That species is notorious for smacking into the glass and doing itself damage, although that can only be a guess here.

 

[TwoTankAmin]

This is from the Google AI so I would take it a bit sckeptically.

Balantiocheilos melanopterus (Bala Shark) shimmying—a twitching, tail-crossing, or rhythmic shaking behavior—is often observed in larger juveniles and adults, frequently occurring after feeding. While it can signify courtship in mature pairs, in most aquarium settings it is interpreted as social behavior or a stress response to water quality

But, I had an adult discus, which was the surviving one of a pair, get spooked and run into the side glass at full speed. Soon after it went nose down and could not resume its normal horizontal orientation. It lived that way for a number of month in its own tank, U di not want ot to be pick on by other fish. It used to feed off of the bottom of the tank.

It never showed any other symptoms, and showed no sign it had been injured or ill in any other way. Intitially. I thought maybe it had a swim bladder issue but was able to rule that out along with most other causes and concluded it had "brain damage,"