Actually, it was once thought that they were blennies, but taxonomists now classify them with the dottybacks. They are aggressive like other dottybacks with the apetite of a grouper. They won't attack sessile invertebrates but will make quick snacks of shrimp and anything moving that fits into their mouths. Therefore, any fish kept with it should be bigger than it can swallow. I've never kept one but saw one on my LFS and have to admit that it's a very cool fish. I've also heard that they have been bred in captivity.