Emerald crab eating coral, advice?

[aydemir]

Hi everyone, unfortunately my 2 new emerald crabs have taken a liking to munching on my corals....

It's been 4 days since I've added them to the tank. One of them has both claws, and the other one (I call him captain hook lol) has just one. Cpt Hook has been munching on quite a bit of coral (pretty much half the time I see him), while the other I have spotted munching on coral I'm not as worried about. The crabs are both fairly small (carapace about 1 inch wide on both).

Some more details; corals that they are munching on are sps birdsnest, acan lords, and a war coral. The coral looking the worst for wear out of the 3 is the acan lord, I can see those white 'guts' stuff sticking out of the head, its only been a couple hours since the latest coral feast for Cpt Hook so maybe that is a factor... In all honesty the birdsnest and war coral look completely fine even though I saw Cpt hook going for polyps, so my theory is that the acan lord is a lot more meaty and easier to grab a hold of to eat which is why the crab is doing more damage to it.

1) So, first question: Have you had emeralds eating corals, and did your corals recover faster than they could eat it?
2) If yes to (1), did you remove the emerald, and if not, how did your corals do?
3) How do you catch an emerald? I do have a fairly small tank but removing the rock would prove quite tricky

Thanks and stay safe everyone!

extra question I just thought of, I've heard some anecdotal evidence on if the crab will be 'reef safe' or not depending on claw tip shape. The rounded claws indicate a crab more likely to go for algae, vs. sharp claws indicate a crab more likely to go for meaty foods (i.e. corals, fish, etc). Thoughts? I have previously had emerald crabs as well but never noticed them eating corals, I'm going to check the claws now.... previous 'good' emeralds were purchased from a different store as well, they may be getting them from different places who knows.

 

[xxkenny90xx]

If they are actually eating coral and not just algea on the corals then do what you have to do to get the crabs out. A diy fish trap will probably work but if not and assuming you can't just catch them then start tearing things apart!

 

[Chefwheredyougo]

Chances are they're just eating algae and small bits of leftover food from your corals, not eating them. That can and does make alot of corals unhappy, though. I thought the same for awhile until I spent the time observing them and decided to let it be. They eventually moved away from the corals but will occasionally come give them a good cleaning.
Observe and make sure they ARE actually taking chunks of flesh from the corals first. If so, your best bet is to remove the rock they're on and grab them from there

 

[aydemir]

Chances are they're just eating algae and small bits of leftover food from your corals, not eating them. That can and does make alot of corals unhappy, though. I thought the same for awhile until I spent the time observing them and decided to let it be. They eventually moved away from the corals but will occasionally come give them a good cleaning.
Observe and make sure they ARE actually taking chunks of flesh from the corals first. If so, your best bet is to remove the rock they're on and grab them from there

Yeah I studied them quite closely and unfortunately it looks like they are just taking actual polyps/flesh

 

[aydemir]

Update: I looked at the one clawed emerald and it does in fact have pointed tips...can't see the other one at the moment it is hiding.

 

[Fishy212]

I had 2 emerald crabs in my tank for over 2 weeks, one I rarely see anymore but it comes out from time to time. I feed the crabs and other inverts in my tank pellets, some mysis shrimp, chopped up clams/mussels and seaweed. Crabs and shrimps are always opportunistic feeders, they will steal food and take them from corals potentially damaging them in the process.

I have heard the same thing about the rounded tip claws as opposed to the pointed tips. Pointed claws are generally more aggressive, most people end up removing them.

Do you have a sump? Try leaving some seaweed next to the acan and hopefully they will go after it and then gradually move the seaweed away.

As far as an easy trap goes a tubaware container will high walls should suffice. Leave a rock or “ladder” up and it will be too tall and slippery for the crab to escape.


Hope this helps!

 

[aydemir]

Thanks for the answers everyone. Was just watching the tank for a bit, and noticed the 2 clawed crab has claws that are definitely more round, and it was just munching on some algae. I also saw the 1 claw crab munching on detritus on the war coral, so I'm going to observe a bit more for now. I still think Cpt hook might have to go to the refugium but I guess I'll give him a few more chances.

Am also still open to more trapping crabs advice lol! Tupperware method sounds promising, not sure if they would go for the food or not if the corals are so tasty...

 

[vetteguy53081]

Dear Emerald:

 

[CWR24]

Love the little suckers, had one years ago, and never had much of a problem with mine.

Until I caught him eating an $80 clam for lunch. You have to get them out unless you like the headache.
And have fun taking them out as it seemed like those little spikes really cling to the rock when wanting to get them off.
More than likely you'll be removing some of the rock work. Be thankful you have a smaller aquarium.

 

[aydemir]

Dear Emerald:

rent is due....:mad:

 

[CWR24]

Dear Emerald:

Most definitely.

 

[|sCRIBe|]

I have had great success using tongs to remove emerald crabs. I have standard size and large long ones with rubber on the ends. I have always been able to grab the crab with the tongs. So one half of the tong is literally in the crabs face and the other half of the tong on the back of the shell.

 

[aydemir]

I have had great success using tongs to remove emerald crabs. I have standard size and large long ones with rubber on the ends. I have always been able to grab the crab with the tongs. So one half of the tong is literally in the crabs face and the other half of the tong on the back of the shell.

Just tried with some tweezers (long tweezers for planted tanks) with no success. Also quite a tight area to work with without knocking over a bunch of corals unfortunately. I may have to resort to trapping or removal of the rock. Really don't want to go with removing the rock but may have to if the coral eating persists...

 

[|sCRIBe|]

Just tried with some tweezers (long tweezers for planted tanks) with no success. Also quite a tight area to work with without knocking over a bunch of corals unfortunately. I may have to resort to trapping or removal of the rock. Really don't want to go with removing the rock but may have to if the coral eating persists...

the large long tongs are best because the opening at the end is wide. tweezers or small tongs will spook them, they can see them. The large tongs work great, if you have them or can get them just be patient and when you see an opportunity get it.