Not that I know of. I haven't seen anything chase the mandarin, and it has gone into the overflow even when the lights were on, not just at night.
This morning before the lights came on I was checking things out with a flashlight. The mandarin was just sleeping on the sand, nothing was around or bothering it. Since the sally lightfoot is out of my tank, the only thing that I'm concerned might bother the mandarin is a large bristle star. But so far, the bristle star has been pretty well behaved as far as I've seen. Whenever I've seen it touch anything live like a crab, it pulls back. I've never seen it try to grab something live.
I think I'm going to try another shrimp in the tank. I had two skunk cleaners dissapear ($30) so I think I'll try a large peppermint shrimp, which will be a little less expensive.