I have no luck with emerald crabs. I put them in the tank, and within a day to a month they become lethargic and eventually die. I'm on my 5th or 6th emerald crab now and I'm just waiting for him to pass at this point. My coral, anemones, snails, hermit crab, and fish are all doing great. Can't keep an emerald crab alive for longer than a month or so. I think the first one I added lasted 24 hours. The next one lasted a week. The next one died when they were pulling it out of the tank at the LFS haha (doesn't really count for me, but whatever). Then I added 4 at once hoping one of them would survive. First one died after about a week. Then a week later another died. Could only find one of the crabs for the next couple weeks then finally spotted the smaller of the two remaining crabs and the next day he was dead too. Thought both crabs were dead so I went to remove the bigger one as well and he started moving around a little bit. They don't seem to move much and they refuse to go on top of the rocks where most of the algae is. They don't ever seem to scavenge any food so I'm wondering if they're just all starving or if something else is killing them? I found bubble algae on two frag plugs, but one was on a frag rack and the other was in the sand so the crabs never made it to them to eat the algae.