I can only tell about the lactoria cornuta, Randy Holmes (Chemistry forum) had one for over two years in his reef with no problems, I asked him a lot of questions before getting mine.
If you get them small, they will get stuck on the filters, mine got stuck all the time when it was small I had to cover the modded MJ1200s. Also mine was one of the first fish to go in with three clowns, this gave the cowfish time to adjust. Another issue with them is if they die they could release a toxin that will wipe out all your fish, this is rare with the lactoria thou.
Mine thinks everything you put in now is food! I have to get couple of table shrimps to keep it busy when I introduce new corals, it did sample a leather coral but that's about it.
Ohh you need to cover your lights specially if they are MH mine spits water out from time to time to get attention!