Emerald Crabs

Has anyone owned or known someone who owned Emerald Crabs?

I have two and when I first put them in, they cleaned the tank WONDERFULLY. One even grew really big and molted his shell (I thought he died unitl I saw this HUGE creature lurking under a nearby rock, haha). Unfortunately, my damsels play a little rough, and my Azure damsel likes to pester them whenever they come out to try an clean. Because of this, my larger Emerald Crab (Oz) dug himself a little burrow under a rock and never comes out more than an inch. He's very protective of his den and keeps it nice and clean. He also attacks hermit crabs and snails who come too near it. Which brings me to my other Emerald Crab.
Elmo is my smaller Emerald Crab and when I placed him in the tank, he immediately started eating away in the middle of a large open area with no regard for safety whatsoever. He was so happy and cute. I guess the other one beat him to all the food though because he stayed small. He too was picked on by my damsels and resorted to hiding. He's a really good hider and I only see him about once or twice a month. In my most recent sighting, I noticed he was missing one claw and two legs. I dont think my damsels are aggressive and would have caused that kind of damage, but I do think if Elmo went too near Oz's den, that Oz could have gotten uber defensive. I would take him out, but I cant ever find him (he's about the size of a dime) and I dont really know who would take a beaten up Emerald Crab

So my questions are:

What should I do about my homebody Oz? I could move the rock, exposing his den and forcing him to go elsewhere. This exposes him to the damsels but they shouldnt mess with him while my hand's in the tank. Should I find some sort of "sunken ship" ornament that he could use as a den that the damsels cant get into?

And the little guy (should I find him again), he seems to be dealing with his injuries fine and healed nicely. Should I make him a den too?

I just want them to be happy

Hmmm...I'm not really sure what to tell you. It's possible that either the damsels or Oz went after Elmo, but who knows? I don't think adding an ornament will help, but maybe. How much rock is in your aquarium? Perhaps if there was more rock, they'd have more crevices to crawl in...

Hmm, I should probably put up those pictures like Don said...I can't tell you exactly how much live rock is there but it's quite a bit. And there are more then enough crevices because I arrange my rock in weird patterns since my damsels like to chase each other in figure eights and in random circles. And I know Elmo finds these crevices, because I never seem to find him.

A pic might help. I don't know how attached you are to your damsels, but have you considered just getting rid of them?

Sam_G wrote:

A pic might help. I don't know how attached you are to your damsels, but have you considered just getting rid of them?

^^Look, I did it!

Everyone suggests I get rid of them and "upgrade to real fish" and I was planning on only using the damsels to cycle my tank. But they're so gosh darn cute! One's a little Yellow Tail and the other's an Azure Damsel. My favorite color's blue Now that I finally got them to get along, they actually play with each other. They play Chase and Tag and Peek-a-Boo (some people think this is actually still terrirorial aggression but it's not aggressive at all. Every now and then I'll see a bit of territorial aggression, especially if my Azure is really hyped up, but these games are not that). They're so cute to watch. I don't think I have the heart to seperate them or give them away

Nice quoting job!

I understand. Once you get attached to fish it's hard to give them up. In that case, you'll need to find another solution for the crab issue...

I've got great news!!!

For the past 3 nights, Oz has come out of his den! I didnt want to come post this right away in case it was a one time thing, but I've seen him on the other side of his rock and even on neighboring rocks!! Im so excited!

He stays on the undersides of rocks or in large crevices to make it harder for the damsels to pick on him, but it looks like he's turning more white. I think he's bulking up on food so he can molt and come back SUPER huge to intimidate the damsels, lol He's already bigger than either of the damsels, but they still pester him. Im not worried about the damsels hurting them, but he could sure to damage to them. Maybe they'll be scared of him after he molts again.

Im so excited he's left his den
...Now where's Elmo? I should've named him Waldo -_-

That is great news!!! Hopefully Elmo will come out soon, too...

careful with emeralds as with any mythrax crab they get pretty damn aggresive when they reach larger sizes and will take on fish. Also they will eat your corals (if you have a reef tank) when they get larger.

Gimplar wrote:

careful with emeralds as with any mythrax crab they get pretty damn aggresive when they reach larger sizes and will take on fish. Also they will eat your corals (if you have a reef tank) when they get larger.

This could explain the ripped fins on my helfrichi...

Wait, they eat corals? How common is this? Mine has never seemed to mess with my corals...yet. But it has recently started eating more around the tank (I was assuming to try and molt again and be even bigger. It's shell has white spots on it.)

Mine have never gone after my corals. Their bodies are only about an 1" wide, though. Maybe when they get bigger it'll be a problem...

So the first time my emerald crab molted, I thought it died. And then, when I saw him again, I thought I had an extra one. I felt really dumb when I remembered they molted. I've been watching my emerald crab for a few weeks now and he keeps looking like he's going to molt, but hasnt. Last night, I saw him hanging off one of the rocks looking dead. Having learned from my past experience, I was excited he molted again. But when I went to move it, it was heavier than I expected. Im wondering if he actually died??? I haven't seen him around, but I know when they molt, their bodies are soft for a while and they hide all the time. So it's possible he's just in hiding? hopefully...

That was 4 days ago. Last night, I found my snail looking like it had fallen over. He does this from time to time. I just right him and he goes along. Only this time I think he's dead. He didn't retreat into his shell when I moved him. I uprighted him and left him for the day to watch, but he hasnt moved. Or come out. I think it's dead.

Why are my things dying??? My coral banded shrimp seems fine (for now). As do my corals and my fish. Neither the snail nor the crab showed signs of being pestered with and they both ate plenty. If anything, I figured they would out live the other tank inhabitants.

If you still have the questionable crab molt/dead crab, (as gross as it may be), try ripping it open and see if it's empty like a molt or if it's not (in which case, that sucks). Maybe just shining a flashlight through it would work...

As for the snail, that sounds like it's dead. That, or it's really apathetic for some reason.

Inverts are the most sensitive, so it doesn't surprise me that your fish seem fine. I guess we need a run down on your parameters. Temp.?, pH?, Alk.?, Salinity?, etc. Have you done anything recently to the tank? Same food, no new additions, same water change schedule, same water source (copper could be an issue...), etc.?

He seemed full the day I found him and empty the day I moved him out of the tank. I no longer have him, but I dont know if he molted or was hollowed out. His bottom plate seemed open, which is why I thought he may have molted out through that hole... but I dont know if that's how they do it.

Yeah, snail's dead. I took him out this morning when I was catching my CBS to return to the store.

Water changes are normal. The only thing I've changed is I added a viaAqua pump to increase circulation. That was about 3 weeks ago and then stopped it Thursday. I cant imagine increased flow would kill my inverts.

I know inverts are sensitive and I thought of copper, but my CBS seemed fine. So do my corals, though my ricordea did turn for the worse about 2 weeks ago. Maybe that was the start? I assummed it was unrelated because he didnt like the new flow.

Nitrite 0
Ammonia 0
Nitrate between 0 and 5

pH 7.9 I know this is a bit low, but that's what my water source is and always has been. Would that really cause two sudden deaths? (I've been looking into pHUP, redsea pH corrector, baking soda and an airstone. Thoughts?)

Your water parameters seem fine. pH at 7.9 is on the low end, but it's not bad. However, pH fluctuates throughout the day and night. So, if 7.9 is at the high peak, and it dips down to 7.6 (or whatever) at night, then you could have a problem; however, if 7.9 is at the low end of the pH spectrum for your aquarium, then your fine. I'm guessing that if your pH is low, it's because your Alkalinity is low. This can be corrected by either more frequent water changes, switching to a salt mix with higher Alk, or adding baking soda or some other additive to your aquarium. I dosed baking soda once or twice a week for almost a year, and it helped a lot (and it's a lot cheaper than the additives that your considering buying ). I used this site to help me figure out the dosage that I needed: http://reef.diesyst.com/chemcalc/chemcalc.html

I don't think it was anything like flow that killed your inverts, but it might be the pH issue. What is your aquarium's temperature? When you say that the pump "stopped", do you mean that it broke (in which case, stray voltage might have zapped your critters)? And, on a side note, why did you return your CBS?

7.9 is what it tests at the end of the day. I've never seen it dip lower, but I always test around the same time (between 10pm and midnight usually). Last time I had Marine Warehouse check my water they said my Alk was "nice and high" but that my calcium was WAY to high. Around 4x the normal level and that it was being held there because my Alk was high. I haven't attempted a remedy for that hoping coraline growth would eventually knock it back down... If I add baking soda to get the pH up, it would raise my alk too, yeah? Im not sure if that's what I want.

My temperature stays at a constant 79F. And I stopped the pump. I unplugged it because none of my corals were opening up all the way. Im still trying to find a way to orient right, between moving it and rearranging the rocks.

I returned my CBS because my damsels fins were getting shredded. Whether it is my damsels picking on the CBS or the CBS attacking my damsels I couldnt figure out, but either way, my damsels were losing.

I don't know what to tell you, Ashley. Maybe get the water tested again by MW or wherever. Everything seems fine. Maybe it was just that there wasn't enough for the snail and crab to eat? Do you have algae growing in your tank?

My reccomendation would be to get rid of the damsels. If they are so aggressive as to cause problems to the emerald crabs then they will be causing you problems in the future. I have 2 large red emerald crabs and nobody messes with them.. even the 9 inch tang or 7 inch angelfish.
I'm quite shocked that a damsel would even try to mess with the emerald crab..

I thought about food being an issue when I put the CBS in a few weeks ago. I thought he might compete with my emerald crab over scraps, but the CBS never left the back wall of the tank (that I saw) so my emerald crab should have had half the tank to still forage. Plus, he always knew just where to be when I feed so that whatever the damsels didnt eat, he gobbled up quickly. I highly doubt that he was starving but perhaps the reduction in diet was just enough to make it not sustainable?

As far as the snail, there is plenty of algae for him to eat (that I now have to clean ). Even a recent (a week and a half ago) bloom in diatom, which he loved to eat. Maybe the bloom was indicative of some drastic change in water parameters?

My damsels actually backed off my emerald crab quite a bit after he started coming out more. AS LONG AS HE DIDNT GO IN ZAZU'S CORNER! Scott would pester him every now and then but it was more for play to see if Scott could get away quick enough. Zazu can get pretty territorial but I intend to rearrange the rocks before I put another fish in so that he wont have a territory to be protective of. I've actually rearranged twice recently since I had to move everything to catch the CBS anyway.

Hmm, maybe the diatoms were indicative of a shift in water parameters. It's hard to say. I guess as long as everything else looks good, I wouldn't worry too much...