It took me about 5 minutes with my hands an a large net (at least 2/3 of the width of your tank). After convincing my domino to one side of the tank, I used the net to block off the other side and I was able to scare it into the net. Then I scooped it out with a plastic cup. My new 125 is pretty light on the rock side right now, so it was not packed with rock. It would have been fun if there were more rock, but I am sure I could have done it. I also made sure that my yellow tang and my scopas tang were in the same blocked off section as the damsel becuase they would block off the rock structure. A fish trap may have been easier, but it kept on nipping on the scopas and sailfin, so the domino had to go.