I received my Black Ghost Knife about 4 days ago. He is small at only 1.5". He has spent the past 4 days hiding in the back corner near the heater. I assumed he was being timid and needed time to adjust to the tank. This morning I was excited for a split second when I saw him near the front of the tank. Then I realized he was lying on the bottom and breathing rapidly. I filled a 1g bucket with clean tap water at the temp of the tank, primed it then transferred the ghost knife. His breathing has seemed to return to a more normal pace but he is still fairly inactive. I am also finishing a large 75% WC as I write this and will return him to the tank when it is done. I know BGK's are supposed to be sensitive when small so I have been monitoring him closely. He hasn't shown any signs of disease with the exception of being shy and not eating. I do weekly 50% plus water changes. Parameters are fine.