Not so harmless acro crabs

[brandyrb]

We purchased a couple of bigger acroporas a couple months back and took them home to find out they had cute little crab residents. The crabs were no bigger than a pea and off-white with blue eyes. Their body shape is similar to an emerald crab.

For a few months these crabs had free reighn in our tank. One of them stayed in the primary coral he came in and I thought he was eating algae off the coral. The other one moved from coral to coral. The primary coral he came in on mysteriously started missing flesh. About half the coral was dying and I just couldn't figure it out. I moved it around in different lighting and we have been very cautious of our water parameters.

Well last night I noticed those cute little pea sized crabs are now the size of a nickel, maybe a little bigger, and they weren't protecting the coral or eating algae! They were eating the coral!!! One of them was moving from coral to coral tearing off the flesh and polyps and eating it. The crabs colors also changed from an off-white to a darker beige/light brown. So my message is beware of cute little acro crabs with blue eyes. They are bad. They are really BAD!

Hey Kevin... do you want them for a non reef tank or should we kill these cute little critters? I really don't want to kill them, but I now know they are the cause for our corals not doing so hot!!! We have pulled two off of our acros and I believe there is one more in there somewhere. I'll be searching for him tonight. The dead give away of the crabs home is the coral mysteriously missing chunks of it's flesh while the other parts are still polyping, that is until the crab has been a resident for a while!

Brandy

 

[jlehigh]

I received the EXACT same blue eyed acro eating crabs in several of my colonies from Bali.. I still have one or two left I havent got to yet. Thankfully my colonies are big enough to handle their appetites..

In addition to the lil blue eyes mine also have a small amount of "hair" on the primary pinchers.

 

[brandyrb]

I didn't take any pictures of the crabs I have, but I did find duplicates on-line. I'm trying to upload them and this is my first time so it might not work.

The crabs are hairy, anywhere from off-white to brown in color and have blue eyes with black tips on their pinchers. My frags unfortunately aren't big enough for their appetite. I'm just glad that they didn't eat the flesh or polyps off my favorite frags which are smaller. They seem to prefer the bigger frags. There is only one coral that might not make it. It is covered in algae right now and I'm hoping it will recover since the hazardous tenant has been evicted.

 

[kevinpo]

Hi Brandy,
Glad you found the culprit. They can be quite destructive. I've only had one of them before. I used a pair of tweezers to get it. The first try I only got a few legs but a week or two later I got him in another coral. The corals quickly recover once the crab is removed.

No I don't have a use for them.

Regards,
Kevin

 

[brandyrb]

Thanks for the reply...

Unfortunately, there is going to be a murder of the cute little blue eyed crabs...

 

[shallowreef]

I killed all crabs that ever came in on my acros. Although everynow and then one did survive and i would just throw them in my Fish only tank where Mr. Trigger fish found them to delightful!

 

[brandyrb]

hmm, I have a hard time killing things unless they are really ugly, so I'm going to let my other half do the dirty work.

Quick question: Is it true that SPS corals will recover more quickly if you put superglue on the dead parts of the coral?

Thanks,

Brandy

 

[shallowreef]

Thats new to me but i wasn't into SPS long enough to learn the secrets to them.

 

[ReefferMan]

redrum.......REDRUM.........hehehe

 

[shallowreef]

LMAO! i loved that movie!

 

[ReefferMan]

Cryogenic Sleep.......

 

[damien_kee]

brandyrb, from your pix, i can c that is harmfull crab.

 

[jake65]

theres a killer amongst us....lol..j/k

 

[ReefferMan]

Wow, Theres not much meat on those crabs, but mmmmm so tasty

 

[JRBear5658]

I have found out the only acro crabs that are good are bandit crabs people call them which are all white (change colors depending on coral most the time) with a black band over the eyes, I will post a pic when my lights come on tomorrow I just bought a frag with one on

 

[BlennyBabe]

Yes the bandit crabs have never caused any problems in my experience. Those blue eyed hairy ones are the devil though. I have had to kill three and they dont make it easy. Best to use a straightened paperclip and spear them. Its just too hard to get them out without damaging the coral. Good luck
They are tricky little buggers

edited because I cant type...

 

[Rod Buehler]

All of the acro crabs are benificial, Especially the smooth porcelin crabs. They keep unwanted parasites at bay, Especially the acro eating flat worms. The little blue eyed guys will munch on the coral itself, but if the coral is large enough, the crab will move on to another spot in the coral leaving the tissue to regenerate in the area that it was munching. If the acro is small, you will want to remove the blue eyed guys, and the can be chased out with a zip tie so they dont have to be murdered.

We realized how important these acro crabs are when everyone started treating for red bugs. The treatment also killed the acro crabs which opened up a new aveneue for the acro eating flat worms, which are a PITA to eradicate.

Shallow Reef, Any time you have a smooth acro crab, whether it be a bandit or any of them actually (except the blue eyed guys), and you want to get them out, Drop me a note and Ill come and get them.

 

[brandyrb]

We already removed the crabs with tweezers and placed them in a zip lock bag with saltwater in it and froze them. I wasn't sure what else to do. The little blue eyed guys don't stay small long and they prefered the bigger corals and did a lot of damage to those corals. They ate the coral faster than the coral tissue could regenerate. I don't think any parasite could eat the coral as fast as those crabs did. I could be wrong though.

 

[victor escobar]

Hi from Spain.

I have had the same experience with two blue eyed crabs, the only difference is that they eat parts of a styllophora and montipora digitata.

I agree that depending on the size of the tank they could eventually be good mates for a SPS but in general terms I wouldn't recommend to have them on purpose.

Sorry for my English

 

[Frankie]

Hey all, thanks for posting this thread. I have my first acro and theres a crab in it. Its the only crab in my tank and i wa a bit freeked about it. But from what im reading, the smooth white or lavender in my case are ok? the tissue seems fine where he is and im not going to frag this acro anytime soon. I really dont care for crabs in my tank but i was hoping not to have to mess with this acro till its bigger.
could i get an id on this coral? Im just learning about sps and going just sps this time. I looked in the coral id section and am guessing its a Acropora_chesterfieldensis