How to catch a nuisance tang?

So I bought a healthy Copperband Butterfly a few days ago and my white cheek tang has reduced it to hanging idol in a corner for 2 days straight. The copperband looks healthy and my LFS had it for a month and it was eating frozen Mysis. The tang doesn't bother the CB as long as it stays in the corner, but move 2 inches from that spot and the tang will go ballistic. I can tell the CB is getting restless and I don't blame him. Nobody should be stuck in a corner this long. I have tried a few things to try to get my tang but no luck so far. I have tried a DIY bottle trap, but he is being on the cautious side and wont go in it far enough to for me to pull him up. It's been in there all day, but I am going to try until the lights go off. I also tried using actual fishermen nets to guide him into last night and I almost had him once, but he found another exit. What should I do now? I am getting really frustrated with my tang as he wont let the CB move. My next idea is to cover the tank with sheets to make it dark (the tank is in our living room with T.V. and we always have some lights on until we go to bed around 10pm. I don't want to wake up to catch him at 3am) and wait until he is sleeping to I can blind him with a flashlight and scoop him up. Hopefully he will be in an easy place to get to. What do I do? It's starting to get to my whole family.