This looks like a decent thread to ask. So what about both wrasses together?
It's quite possible if one is introduced correctly to the other, or if introduced at the same time.
Mine was a perfect citizen. Only till my tank crashed and I looked for another one on line and found it under non- reef safe wrasses did I find out that it was categorized as such. I was very surprised.
None of the mentioned species are not reef safe; they're all reef safe with caution. They won't harm corals, but they do pose a risk to ornamental invertebrates.
I suppose I was a bit cryptic in my earlier response; I'll elaborate.
H. melanurus, H. ornatissimus, H. biocellatus, and H. claudia all pose a risk to feather dusters. It's variable with any given specimen; some will go after them, others won't give them a second look. It's all a luck of the draw here.
How much of a taste for hermits/crabs or snails H. melanurus has is also quite variable. Some will leave both alone, but most generally find one or the other tasty. And a small percentage will find both tasty, and will regularly go after both. Shrimp are generally safe, but some eat those too.
H. biocellatus is the most mild-mannered of the Halichoeres which might be labeled as a "Christmas wrasse". To me, these are the "Red-lined wrasse", but this is why common names are subjective. Most specimens here will leave your hermits/crabs/snails alone, but there's always exceptions here. Regardless, very rarely will this species decimate your CUC; the safest bet of the bunch. Shrimp are almost always safe with them.
H. claudia only carries a slightly higher risk, and this is the "true" "Christmas wrasse" to me. These get a little larger then H. biocellatus when full grown. Again, they don't generally develop a problematic taste for your CUC, but do expect them to "treat" themselves once in a while. There's a small chance shrimp might be on the menu.
H. ornatissimus, or the "Ornate Wrasse" as far as I'm concerned, gets big, can get mean, and generally gets quite hungry. When these guys get big, any ornamental invertebrate is on the menu. When they're small, they should be somewhat well behaved, but this won't last. With size comes appetite, so don't expect to keep a steady CUC with this guy. And as I said, also with that size usually comes attitude. I'd steer away from this one in a reef tank.