Once, years ago, I walked in the LFS and saw the coolest "Royal Gramma" I had ever seen. I got it home and placed him in my tank. That night I watched him beat the living bejesus out of everything. Turned out it was a Bicolor Pseudochromis, which in English means "The Fish only Satan could love". Oh man was he a terror. I had him in a 180 gallon and there was no freaking way I was going to break that tank down just to catch one stinking fish.
I'll tell you how I got him out. I placed a cube of frozen brine shrimp in my fish net and placed it in the tank. As the shrimp thawed, it drifted out and fed the tank. I had to do this for about a week, but once my evil bi-color got used to the net, he started racing into it to grab all of the food. One day I set the net in the water; he went in; and I yanked the net out of the tank..carrying about 3 gallons of water mind you...but I had him!!!!