Harlequin Tusk not eating

[JStorey]

I have had a Harlequin Tusk for about 9 months now and has been doing great. For the past week he hasn't eaten when normally he eats like a pig. there are no eternal signs of parasites I can see and he was breathing normally and acting normally until today. He is in a cave at the back of the tank and didn't come out to feed. I can see him and he is breathing but not moving. Any ideas on what might be wrong? All parameters are fine and I haven't added any new fish in over 6 months.

 

[Percula9]

I have had this happen to me, fish stops eating for no apparent reason. Add some garlic extreme to the food and water, hopefully this will stimulate his appetite.