I do not know if this question is "answerable", but if it is, I figure you are the guy to answer it. I also realize it is beyond the usual scope of this thread.
Is there an average time it takes for a fish to feel "at home" in a new tank? In other words, before they start displaying their true behaviors or aggressiveness?
I had asked about adding a flame hawkfish to my 39 gallon bullet-shaped tank, and was worried about it having issues with my yellow watchman goby.
You said you didn't see any problem, and things were wonderful between them. Almost 30 days to the day after introducing them, literally out of nowhere, the hawk suddenly started attacking the YWG, killing it in a matter of minutes before I could do anything to stop it.
I am very surprised and very disappointed. These fish do not occupy the same ecological niche and should not interact. The only thing I can think of is that the goby was protecting a pistol shrimp that the hawkfish wanted to eat. I am so very sorry that my advice caused you to lose a fish. 
I realize every fish has their own behavior above and beyond species generalizations, and certainly knew that was a definite possible outcome, I'm just curious if there is "honeymoon" period of sorts where fish do not feel comfortable enough in a new environment to start sorting out territories or hierarchy levels. Similarly, there are several fish that we always are told to "add last". Does this also play into the equation there?
When I tell someone to add the fish last, I am trying to avoid the fish (e.g. a yellow tang) from establishing itself and claiming territory. The "new kid on the block", for a while at least, will feel insecure.
I greatly appreciate all of your advice, and the service you do for everyone here at Reef Central!
