Arowana holes/indents on head

[Ben01]

Hi all, I'm new to these forums and looking for help/any advice on caring for my arowana. I've had several arowanas for years but have not yet encountered this issue.
Recently some small holes/indents appeared on my arowana's head (see attached pictures). I'm not sure what is the cause or how to treat it.
Any ideas/thoughts/suggestions/advice would be greatly appreciated!
Thanks in advance!

 

[philipraposo1982]

I believe your arowana has hith. Hole in the head disease.

 

[duanes]

Typical hole in the head lesions, most often due to lack of enough water changes, or other stress, like hard water, high pH (they are generally soft water species) abussive tank mates, in too small at tank, etc etc.
Adding tannins to new water, with an increase in number and amount of water changed could help, but it will be a long road to repair those scars.
If it were me, I'd be changing 30-50% of the tanks water every day, until its under control.

 

[RD.]

Asian aros do not get HITH from hard water, or high pH.

These are highly domesticated strains of fish that are commonly grown out in ponds in Singapore where the pH is 7.8 ish. That, and I have seen countless Asian aros grown out in hard water, with pH of 8.0, for many years (30+ inch specimens), with no issues.

Some form of stress would have triggered the outbreak, possibly quality of water (nitrates/ammonia), with the culprit most likely introducing the pathogen involved (Spironucleus vortens) coming from the Angel fish. I would improve water quality, while also treating for Spiro/Hex.