Datnoid Disease?

[Odo]

Have you tested your water?

Yes

If I did not test my water...

1. ...I recognize that I will likely be asked to do a test, and that water tests are critical for solving freshwater health problems.

Do you do water changes?

Yes

If I do not change my water...

1. ...I recognize that I will likely be recommended to do a water change, and water changes are critical for preventing future freshwater health problems.

I came back today to find my datnoid hasn’t been eating and has marks all around his head, gills etc

Does anyone have any idea of what I’m dealing with?

 

[Rocksor]

Could be aggression issues from the other fish when you are not around, which leads to it being beat on or the datnoid running into the driftwood trying to escape. Another possibility is it getting spook and hitting the driftwood.

 

[krichardson]

I'm not the best at diagnosing fish ailments but it looks as your indo is suffering from some kind of bacterial infection.