I recently had an experience with one of these. I added one to my 180 gallon fish only tank. After an hour he got really aggressive with my porcupine puffer. Within minutes I could tell that one fish would have to be removed or the puffer would die. Since my puffer is by far the coolest fish ever, I took the wrasse out and took him back to the LFS, who was nice enough to credit me, even after my 3 week QT. So I think these tend to be a bit more aggressive than than most wrasses. I have a Klunzinger (sp?) wrasse in another tank, which is a closely related fish. Still aggressive, but not nearly as aggressive.