My serpae tetra swims in a weird way

[Garygilmoreseyes]

My mum calls my serpae tetra “gimpy” because he swims in a weird manner. I’ve researched and he doesn’t swim like he has a bladder diseas but he has a tough time staying upright. Every time he swims, his lower back falls and he has to twitch back up to be straight. Is there something wrong with him or does he have a bad fun? He seems healthy and social. I’m just concerned he might pass away soon

 

[JemZ]

Could you post a video? Your issue sounds identical to the problem I had with my serpae tetra, and in the end, I had to euthanize him. But don't euthanize him until we know what is going on. If it is swim bladder, feeding him a cooked, deshelled pea may help to flush out his stomach.