i do have a reef tank. i had my paramaters tested when i bought the fish and everything was dead on, salinity, alcalinity, calcium were all perfect. I have an emerald crab, and i'm assuming he did the damage that i mentioned (fins eaten, gills damaged, etc.) the only fish i can think of that was pretty territorial is my flame hawk. i let the bag sit in the tank for 25 mins to acclimate temerature. every 5-8 mins i put in a little water into the bag, roughly an ounce or two each time until i double in volume. i let him sit for another 10 mins after that to acclimate, then get a lot of the water out and slide him in trying now to get any water in my tank. he acclimated ok, swam around, checked stuff out for the first couple of hours, then started to hide. i ararely saw him for the first 48 hours and then came out a lot and started eating. thought he would have been ok. of course the next day was when I found him dead and eaten lol