Half my Ram's face is black!

[Sandy Beach]

Overnight his face went black on one side. He seems to acting normally otherwise. No other issues in tank. About 4 days now, seems a lot darker now.
What do you think it is?

 

[Ichthys]

Nerve damage. The Tropical Fishlopaedia (every aquarist should have a copy) says this…

Abnormally dark coloration is a very common sign of stress but may also be seen during many other diseases…
Heightened or otherwise abnormal coloration may be a sign of damage to the central nervous system with resulting loss of control of the chromatophores. Possible causes are hypoxia, poisoning, acidosis / alkalosis, injury, bacterial infection, or tumour.

It can kill the fish but in most cases (ime) it’s either temporary or stays but does no harm. I’ve treated this before with a bactericide, which worked in a couple of cases

 

[GaryE]

I have seen it, and had it stay for the lifetime of the fish. I questioned whether the injury involved could have been a stroke affecting blood supply or the nerves of the face. Since Cichlids control their colours, an injury could do that.

Nothing died prematurely from it here (only maybe 3 fish in decades) and I only ever saw it with SA Cichlids.

It only affected individuals, and then, newly arrived ones. So injury in transport was another suspect. I hope in the case of your fish that it's something benign.

 

[Ichthys]

I only ever saw it with SA Cichlids.

That’s interesting. I can’t remember if I’ve seen it on others or not…

And when I said it can kill, that could well have been caused by the bigger issue that caused the damage (the infection, or secondary infection, or whatever) rather than the discolouring itself. Mostly the discolouring itself seems “benign”.

 

[GaryE]

I was once told it could be an infection of the nasal passages, given that Cichlids have nostrils. The theory was it caused nerve damage. Could be.

I kept a lot of SA Cichlids and nowhere near as many Cichlids from other regions, so my sample may be small.

 

[Colin_T]

chemical poisoning, its like a bruise on us

give it clean water and a clean tank and it should fade over a month