Naso tang showing rib cage and spine today yesterday looked normal I have no clue what’s going on

[joshjp1999]

Hi guys thank you for helping I have a naso tang he was very healthy and happy until I got home tonight for some reason his hole rib cage is showing and it’s really scaring me this morning when I had left for work I left him a nice size of algae for him to graze on while I was gone when I returned home I seen he had ate all the algae so I gave him more for him to graze since tangs constantly graze and then I noticed his hole rib cage showing hopefully you’ll be able to see in video I’m gonna post but I always have food for him readily available in the tank thank you guys for the help hope I can figure this thing out.

 

[joshjp1999]

video and picture of food posted and i also just noticed its more visible on one side of his body than the other hoping it isn't an internal parasite