Urgent!

[Schaumer]

Hey
As I was doing my water change on my tank I had noticed one of golden dojo loaches with a one red eye.
, please help as I'm not sure what to do and this guy is my favourite fish in the tank. I tried to upload a pic but the file is too big and I can't make it smaller.

 

[Blondielovesfish]

Is it possible that this Dojo Loach has always had it but you just haven't noticed it? 
It could have been caused by something sharp in your tank or by another fish.
I'm not really sure on this but they are just my suggestions.

 

[the_lock_man]

It could be any number of things.
 
What are your current water stats (ammonia, nitrite, nitrate, pH)?
What other fish are in the tank?
How long has the tank been set up?
Anything else that's new in the tank?