Gray spot on the lower back fin of my GNM?

[meir]

I would test for ammonia and get an air stone in the tank if you can. If you have ammonia in the tank, do at least a 50% water change and add Seachem Prime.

Already tested, there doesn't seem to be anything wrong with my basic parameters

 

[bios]

@meir do you run ozone?

 

[meir]

No @bios, why?

 

[bios]

I saw same symptoms in tank runing too much ozone

 

[meir]

@bios like...? I don't run anything other then internal power pumps and hob filter

 

[Reef_Collector28]

Looks totally fine, sometimes they might chase each other and one might bite or nudge the other. Also might be she rubbed against a rock or something at night. Spots like that have gone away when ever my clown had them.