Crab in Acro - Good or Bad?

[Beverly]

Have noticed a tiny white/clearish crab, with one claw bigger than the other, on the base of an acropora I bought last week for my 37g lit by a 175w MH. Is this crab going to harm my coral?

Sorry for what might seem like a very dumb question, but I have never kept acros before :redface:

[Willow]

sounds like an acro crab. good commensile crab that lives within acro colonies.

[Willow]

sorry i should have asked what your magnesium levels are first :P

[Xtasia]

I heard they were ok b/c they keep the acropora clear of detritus. I have one with one tan crab, and another with 2 whitish ones. All's good 6 months now.

Wet web media says:
Hello,
Are the small crabs found in Acropora harmful to the coral?
>>
Not generally... all else being equal they're of no consequence.
Bob Fenner

Reefs.org has more info...
http://www.reefs.org/hhfaq/pages/main_pages/faq_livestock.htm

I just bought a colony of Acropora/Pocillopora and there is a crab living in it. Is it harmful?
Chances are that the crab you have found will not be a problem. Crabs found in heads of SPS corals are usually of the Family Xanthidae. They are typically commensals which sometimes protect the coral from predatory fish or invertebrates. However, all of these crabs should be watched carefully as not all of the Xanthids are harmless - see below. Trapezia sp. (Family Trapeziidae) is usually found in Pocilloporadae while species such as Tetralia and Domecia (Family Xanthidae) are the typical residents of Acroporidae.(Delbeek and Sprung The Reef Aquarium, Vol. II, pg. 324). In the experience of the author and other reefkeepers that the author has conversed with, hairy brown crabs imported in SPS colonies tend to be harmful rather than commensal, while the tan, smooth shelled crabs like the one in the above picture are peaceful, well-behaved residents.

HTH

[Chin_Lee]

sorry i should have asked what your magnesium levels are first :P

:lol: :lol: :lol: almost made me spit out my coffee!!!



Beverly, keep in mind if you ever treat with interceptor, your crabs will not make it. If you need to treat with interceptor, try to get them out of the acro which is almost near impossible depending on the size of the colony.

[Beverly]

Thanks Willow and Xtasia for the replies and the link :) My crab looks something like the one in the pic.

Willow, don't actually know Mg levels in my tanks. Has been awhile since I last tested chemistry in all our reefs ;) How's the Mg in your tank(s) :razz:

[GMGQ]

Quick rule of thumbs on these hitch hiker crabs:

HAIRY = BAD
Smooth = GOOD

I found 2 smooth ones in my big Yellow/Green Porcillipora the next day after I brought it home :)

[Manny]

i have those crabs in almost every one of my acros and one in my milli. they seem to be harmless and i would seem to be under the impresion that they are benifficial because the acro is its home.:)

[muck]

sorry i should have asked what your magnesium levels are first :P

:lol: :lol: :lol: almost made me spit out my coffee!!!

:rofl: Thats too funny!!

[Winters]

Well, I recently acquired an Acro piece with this crab in it:

http://i6.photobucket.com/albums/y215/ihayat2/Aquarium_Gallery/2005_December/Acroporacommensalcrab.jpg

It does look a bit 'hairy'. People have advised me that it's probably okay. Thought I'd get another opinion. I'm assuming this is what is considered "hairy"?

Take care!

[muck]

That looks like it might be the same as what Tony described that he had.
Get him to confirm it but, Im thinking that is an acro muncher.. :twised:

[mr_alberta]

I had one of those too in my Bali. It had blue eyes and hairy legs. I got him outta there pretty quick!

[geopod]

Hi Bev, Havent talked to you in awhile.I have heard both sides of the fence that acro crunchers will actually clean the detrus off but also cleans too much and the acro stars to peel.And by then I heard it was too late. But I also heard that some are ok...If it isnt a hermit I get rid of them now after my loses with the big red eyed crabs that ate my starfish and corals.Even found zebra crabs eating my snails......GONE...no more crabs. I guess it is your choice .Lots of good advice from others here.Take care and Happyu New Year....

george

[michika]

If its hairy and has bright light blue eyes, its an acro muncher...remove it quick because once it starts eating your acro, RTN is usually quick to follow. I've already had this terrible experience once, and I really don't want anyone else to have it too!

[saltynuts]

their is a thread on rc. sps section
they eat the polyps of acros so get him out fast.
if i find it i well post it!found it
http://www.reefcentral.com/forums/showthread.php?s=&threadid=740329

[Delphinus]

Hi Ed, thanks for the link. That's the exact same crab I posted about a week or two ago who was munching the polyps on my acros. In my case, I can confirm he was munching down polyps. It was as if the polyps were cut shorter with a lawn mower.

[saltynuts]

your welcome