There is a good chance this fish will cause problems in a reef aquarium. They are fond of tubeworms, but in our experience, don't eat corals.
This fish poses a threat to small crabs and shrimps.
Don't let the small size as a juvenile fool you - these fish can grow very large.
This fish often has a fun and interesting personality.
We keep a Yellow Boxfish, Bruno, in one of our soft coral tables, he’s trusted being in the same tank as several hundred pounds worth of coral. Before then, he lived in a small mixed reef aquarium with a couple of small Pyjama Cardinals. He’s never touched any of the corals. We’ve not had any reports of eating corals from any customers of ours either. But our experience is of a handful of fish, so please do your research before buying this fish.
They are also said to produce a toxin when stressed, and will release the toxin when they die, and wipe out the tank. Again, this is something we’ve not witnessed happening, and in the few documented cases online, it’s not clear whether the wipe out was caused by the Boxfish specifically, or larger problems with the tank. That is, something caused the Boxfish to die, so it is reasonable to think that other fish might die of the same cause. But again, please do your research before buying this fish.