I think that crabs are so cool, but I've always kept snails because I've heard that crabs are opportunistic. Well, I bought a decently sized emerald crab ( first mistake ) about a month ago, and he hasn't been too bad, until today. Here is what I don't like about my emerald crab specifically. 1. He knocks over all of my frags ( expected ) 2. He ate my darth maul Zoas ( kind of expected) 3. He's been picking on my smaller nassarius ( expected ) and finally, 4. He ate my 3.5 inch black sailfin blenny I just got! I got the fish about 3 weeks ago, he was thin, but started eating everything after 2 days ( algae, nori, flake, pellet, frozen ). He had 1 small bout of ich, but recovered nicely. He was doing great, so I am 95% sure he didn't die of natural causes. The emerald crabs punishment, death by mantis in a few months when I set up that tank. Feel free to donate your convict invertebrates to the mantis colliseum if you want lol