I recently purchased a bangai cardinal and a peppermint shrimp for my 20gal hex. I already had a yellow clown goby and a Blackmouth Bicolor Chromis. The cardinal never left the bottom of the tank (almost touching the sand). He never ate or explored the rockwork. I once saw him float to the top of the tank and stare out for a few minutes, so i tested the water quality to make sure I wasnt suffocating him with ammonia or high nitrates and all of my tests came back great. my nitrates were at about 10 and everything else was great. Is it likely that this fish was being harassed by the chromis? I once saw the chromis chase the cardinal when he got too close to the rock work. After 3 days the cardinal layed over and died in about 5 minutes. he was among many other cardinals at the LFS and they all looked really healthy. they were all tankbred. what was wrong with this fish?