i have 2 black ghost fish in a 95 gal tank with discus. Its been 6 months i have had these. One of the black ghost is swimming the entire day no hiding what so ever. But its not eating. No signs of anything unusual on its body, it just not eating. What could be going on? The other ghost fish is eating and everything but that one is about 7 inches long. This one is about 4 inches long. Water temp is 78, 0 ammonia, 0 nitrate, 0 nitrate, and ph is 7.0.