Bending Bala

[ARD]

I've trawled the net but cannot find a specific answer so wondered if anyone on here might know what is the problem.

Basically one of my Balas seems to have a slight indent on one side, and it swims sort of in circles favouring that side.

It eats well, not constipated etc. No sign of any marks, spots, scale damage etc.

Water all good, no spikes, changed 50% yesterday, but it was still well within range prior to. Temperature is 26.8 C

All other fish are fine.

The Bala does not seem in any discomfort or stress.

Many thanks

 

[Delapool]

A little stumped. It looks fairly deep into the body and not just under scales? Also was the nearby fin red at base.

 

[ARD]

I don't think the fin is red at the base, looks the same as the other Bala. Hopefully this short video might help. Forgive the excessive air bubble, did a water change so just pounding the air for a while

https://youtu.be/uNL0axj4yC4