I have a 4 month old niger trigger in a 55 gallon fish only tank. He has not ate in 3 days and is hiding to where I cant get a picture. My ammonia is 0, along with the nitate and nitrite. The ph is 7.8. The salinity is 2.6. temp in tank says 76. The only other fish are 2 damsels and a purple dottyback and they are fine. Please help