Missing scales/ colouration on green chromis's head

[Pocelo]

I have had 3 green chromis for around a month and they are the only livestock i have in the tank.

Initially, the biggest chromis had a small spot on his head that was missing some scales. I didn't think much of it as i thought they were just bumping onto the rocks. However, i did not notice any of that behaviour. Recently, it became worse and the whole head from the mouth to above the eyes are missing scales. Any possible reasons as to why? He is still very active and eating well.

 

[Jay Hemdal Verified Community Expert]

Welcome to Reef2Reef!

Although this species does not often develop it, this seems like Head and lateral Line Erosion (HLLE). There is a similar condition called "Epithelial Thinning" that this also could be. Both issues seem to be caused by environmental issues and are not really fatal to the fish, just make them look bad.

Here is an article that I wrote about it:

https://www.reef2reef.com/ams/head-and-lateral-line-erosion-hlle.784/

Jay