I've tried the time-out in my QT for a week while I rearrange rockwork/territories twice and neither time worked out for me. Once was for a blue damsel that I honestly knew better than to put in my tank; he was ejected pretty quickly for harassing my clowns. Second one was McMurderFace, also known as my powder blue tang. He killed my male clown and a chromis and was working on the midas blenny before I got him with a fish trap. I wanted to keep him so badly and really, really hoped the new aquascape and a cool-off period would fix things, but he was back to being a jerk two or three days after he went back in. Luckily the LFS was very happy to take him for store credit. I was pretty embarrassed about taking him in, but my LFS was great about it, and if I ever end up with a bad match again, I'd be faster to trade the aggressor in. If you're really attached to the blenny (and you have a fish trap on hand so you don't have to pull rockwork a second time if it doesn't work) then go ahead and give it a try, but if you're more attached to your clowns then honestly I'd skip straight to rehoming/trying to trade to your LFS. Alternatively, if you have a big sump and rocks/macro in it with minimal equipment, that could just be his permanent home.