Generally 2-4 weeks, you can use the damsel, most people say it's cruel and what not, but a 3 stripe will be fine, don't add the shrimp with the 3 stripe though, he will be enough. Get a test kit and test your ammonia nitrites and nitrates. When you have 0 ammonia, 0 nitrites, and 20+ nitrates, do a large water change and you should be good, there's a little more to it than that but that's the short version, read up on it while you wait, I've heard this many times on here and I believe it - " nothing good happens fast in a reef tank"