Red Dragon and Emerald Crab gone rogue!

golfnut1232 · Mar 11, 2014

I have two emerald crabs in my tank, one large and one smaller. The large one decided he liked the taste of the growth tips on my Red Dragon acro! It was a sight to see I tell you. Really ticked me off. Tried for a few days to catch him and finally got him last night and he's got one leg less from a previous attempt to catch him. His punishment? He has been thrown in the dungeon (sump) forever! I thought to myself, how much bigger would my red dragon frag be by now if he hadn't be chomping down the tips?? Anyways, an fyi to all of you with emerald crabs. I didn't see him bothering any of the other sps in my tank.

ritter6788 · Mar 11, 2014

They are strange creatures. I had several in my tanks with no issues then one day caught one picking at the tentacles of a bubble tip anemone. They did eliminate all my bubble algae though.

watchguy123 · Mar 11, 2014

Emerald crabs sometimes hang in my mr. packman, which is very similar to the red dragon. I am sure the branches and/or tips probably collect or snag stuff that flows by and that is what interests the emerald crab. If the tips of your red dragon are dying, however, then the crabs may be interested in the decaying or algae infested tips. So, I think you can probably reprieve your emerald crab from the sump and throw him back in the display. I doubt they are eating healthy coral tissue unless perhaps starving.

Here is a pic of the packman acro but I did not take find the emerald in there when I took the photo. But you can get an idea of what I mean by how the dense branches may collect stuff flowing in the water, at least enough of something that your emeralds like.

evolved · Mar 11, 2014

I once had an emerald snaps the tips off an acro; I watched him do it one evening after suspecting him the day before. It was a healthy, cali tort too. The tips were new grow tips.

I've never kept emerald's again after that experience.

Russellaqua · Mar 11, 2014

I never had an issue with them, but I've heard so many stories from people that have that it makes me think that your chances have having a model citizen is about 50/50 with them. They're like any other creature with a brain. They all have their own individual personalities.

rossco · Mar 11, 2014

One of my larger emeralds found his way to my mp40 and was cleaning it pretty well. Later that day he was at the front of the tank and the movable half of one of his claws is gone. Must have reached a little too far into the pump.

rocknut · Mar 11, 2014

I was told that the males were much more likely to pick at coral? I remember a thread about this a long time ago, also gave some photos showing how to determine male vs female. I have had two Emeralds over the years, and both gave me trouble. The last time I tried, the crab was seriously perched on top of an SPS frag within 5 minutes of adding him to the tank, pulling at the polyps...

KoleTang · Mar 11, 2014

I haven't kept emeralds ever since one went to town on my acros. It ate half of a green slimer frag in a couple of hours.

BuGG · Mar 11, 2014

Same horror story here. My emerald crab decided to munch on a duncan and pocillopora.

skiwez · Mar 11, 2014

I used to be a big fan of them, had a tank along time ago and they very judiciously cleaned the live rock and in between corals but they were always very small crabs. Just recently set up a new tank and the guy at the LFS gave me the biggest emerald crab I had ever seen. Had to be about the size of a quarter. didn't realize it at the time because I bought a bunch of CUC that day. Anyway fast forward about two week noticed my zoa's closed up a lot and missing a couple of polyps. Thought it was odd, but didn't really give it much thought until I spotted that emerald crab on top of the plug slowly chomping away. watched the little bugger very delicately eat 4 zoas bit by bit. Was kinda entertaining because at first I didn't believe it especially since he only had one claw. He too is now banished into the sump. I may allow him back up after the zoas establish themselves but not yet since it's a relatively new tank.

golfnut1232 · Mar 11, 2014

Interesting to see all of your responses. Watchguy, he was actually breaking the tips off. The red dragon has been doing very well, encrusting and polyp extension better by 50 percent from when I put it in the tank. Also nice growth tips. So, no doubt I have a emerald crab gone bad. Plus, by the looks of the other posts, it's definitely a possiblility that it may have acquired a taste for sps. I try to feed the fish often, but I don't target the emerald specifically so starvation I guess could be a possibility. By the way, sweet pacman colony. Very impressive.

watchguy123 · Mar 12, 2014

Golfnut, I am actually amazed by the responses as well. I ended up googling the issue and live aquaria states it is a possibility as well. I assumed as I was reading each account, that the corals that were being consumed were dying first and then having decaying tissue eaten. But it seems I may have been too adamant in my initial statement. It seems emeralds may go rogue after all We all are easily fooled by our own limited experiences. One of the great things about reef forums is that we get an opportunity to share experiences. Now how am I going to catch those emeralds

golfnut1232 · Mar 12, 2014

I was able to catch mine with some 18" stainless tweezers that I use to grab coral when needed. Took me a couple of trys, but eventually nabbed him. I missed for a few days cause they definitely grab the rock strongly, so if you don't get him the first time when he's out in the open, he'll then quickly hide and you have to wait for the next time he's in the open. Patience is key. Just don't break a huge piece of that pacman off in the process of trying to snag them! :neutral: