Experiences with emerald crabs?

[fandaga]

I only had one. It immediately started eating a stylophora but wouldn’t touch the bubble algae. I moved it to another tank and then the stylo recovered after about 6 months.

 

[Billgasser]

Had 1 trim my Duncan’s. Another cut the top off an Oregon Tort.
Rarely have I seen them eat my Bubble Algae.
Not a fan

 

[FernBluffReef]

Define success?

I have several emeralds in both tanks.

They have not wiped out bubbles as much as I’ve hoped but it’s not bad either. IDK if they are eating or if my tangs do but the tanks are relatively clear. I rarely see them but I know where some live.


They have not caused any damage to my knowledge. Either. Only potential offense is My dersa clam keeps randomly closing and an emerald has made its home in a cave who’s entrance is basically the clam - so I’m not sure if the crab is on occasion bothering the clam or what.

 

[Grog]

Never had any problems with them, other than my wrasse killing them if they are too bold and come out of safe spots. (My lunare does a number on my cleanup crew but he's my favorite fish so he's not going anywhere.)

I do think that sometimes the crabs are cleaning algae and detritus off of the corals, and people mistakenly think they are munching on coral. Yeah, the corals get irritated but long term, I think they are doing a necessary job. I'm certain that some might eat coral, but that has not been my experience. Then again, I feed heavily, so maybe I'm just providing them with other things to eat that are tastier and/or easier to forage than corals.

I have one that likes to use my stylo colony to hide in. (probably hiding from the lunare). It clings to the bottom of the stalks, and blends in really well. The stylos are tall enough that their tops have shaded the base, so he isn't doing any harm down there.

Are they perfect, no, but I do think they serve a purpose in my systems. I've become more of a fan of pythos crabs these days as they seem to do a better job of keeping things clean, but I still keep a mix of both, just for varieties sake.

 

[bubba005]

Never had any problems with them, other than my wrasse killing them if they are too bold and come out of safe spots. (My lunare does a number on my cleanup crew but he's my favorite fish so he's not going anywhere.)

I do think that sometimes the crabs are cleaning algae and detritus off of the corals, and people mistakenly think they are munching on coral. Yeah, the corals get irritated but long term, I think they are doing a necessary job. I'm certain that some might eat coral, but that has not been my experience. Then again, I feed heavily, so maybe I'm just providing them with other things to eat that are tastier and/or easier to forage than corals.

I have one that likes to use my stylo colony to hide in. (probably hiding from the lunare). It clings to the bottom of the stalks, and blends in really well. The stylos are tall enough that their tops have shaded the base, so he isn't doing any harm down there.

Are they perfect, no, but I do think they serve a purpose in my systems. I've become more of a fan of pythos crabs these days as they seem to do a better job of keeping things clean, but I still keep a mix of both, just for varieties sake.

Just peeked in on my new one and she was on top of my devils hand and looked to be picking off of it, but without doing any damage. I’ve also noticed my female emerald in my other tank doing the same thing on a toadstool, so I really think they’re just picking off whatever crap may be accumulating on there

 

[twentyleagues]

Just peeked in on my new one and she was on top of my devils hand and looked to be picking off of it, but without doing any damage. I’ve also noticed my female emerald in my other tank doing the same thing on a toadstool, so I really think they’re just picking off whatever crap may be accumulating on there

That is very possible. I caught all 3 of mine at night/early morning in the dark at different times actually shredding perfectly healthy acan frags. Literally pulling pieces of flesh off and eating it.

 

[bubba005]

That is very possible. I caught all 3 of mine at night/early morning in the dark at different times actually shredding perfectly healthy acan frags. Literally pulling pieces of flesh off and eating it.

She didn’t hurt it at all thankfully. This morning she was picking one of my zoa frags but left the actual flesh alone. Seems like she was just cleaning algae near it

 

[bubba005]

Looks like she’s doing her job!

 

[tryingtoreef]

I had one in my 29 gallon. Ate all of the bubble algae, then it wasn't long before he decided to take a little off the top of my pavona. Decided he didn't like the pavona anymore and left it alone for the last couple of months. A week ago he ate about a one inch chunk off of a toadstool.
To the sump he went

 

[Xefan]

My Emerald has been nothing but great, and I even moved him into my Nano for 6 weeks whilst I treated for acro red bugs and he was fine there too.

I honestly wonder if people believing emeralds are eating their acros are misreading it, I got STN on an acro where it was losing flesh from the base I'm pretty sure because of the red bugs triggering weakness/infection, after the STN started the emerald was picking at the area of receding flesh, but once I stabilised it and stopped the STN he never went near it again. Frankly I think he was just picking the dead flesh, or the pests, or algae that was growing on the dying parts of the coral. I can see why some folks might therefore see that and think the crab is the cause. The surviving piece of acro is still in the tank and has fully recovered, and the crab has never gone near that or any other.

In fact the only thing I think he might have killed was his female companion who I found dead after about 3 months with him nearby, and they usually kept at opposite end of the tanks so had no interest in each other. He has completely and utterly eliminated both green hair and bubble algae from my aquarium.

 

[feelingfishy]

The reason I said that I believe a large emerald attacked my homewrecker, is because it was physically the only thing in the tank at the time that could literally take a chunk of skeleton off the frag. I found a chunk of skeleton literally on the sand bed. And I had just recently introduced the emeralds as well.
I should have made my post more clear.

 

[Crabs+Shrimps-69]

The better option is a Percnon Gibessi. Way and way more reef safe. One of those guys cleaned my bubble algae in a matter of days in my 15G. Now it's just chilling in my 25G. They do get rather big, so you do probably have to trade it in after a few months.

Aren't they just sally light foot decorators?
Didn't know they eat bubble algae!

 

[Gregpetro]

I haven't had any problems with mine in my mixed reef. She's cool and does a ok job cleaing. But I got a female because supposedly they are more reef friendly. Tho now that things have grown out i never see her. Occasionally I see her malted skeleton.

 

[Grog]

Here is an action shot of one of my crabs eating bubble algae that was in a zoa colony.

Zoas were not happy being climbed on, but you can see he clearly has the bubble algae in his mouth and claws. :cool:

Fun when you can catch them in the act. I always wondered if they were doing the job they were hired for.

 

[elysics]

Had a female emerald that was doing great for years.

After that one was gone and dealing with bubble algae and a dictyota plague for a while I got another one, this time a male. It got the algae under control, but when it got a bit older it also went on an extermination spree against all small snails. Went from hundreds of columbellas to a single one, lost all stomatellas, and it probably is the reason I lost a few peppermint shrimp as well.

I could see it pouncing stomatellas like a cat it's prey and rip them from the rocks.

All I could ever see the female doing in the past was picking at a pocillopora a bit, but doing so little damage that the coral didn't even develop dead spots and just outgrew the problem, and it didn't bother the snails.