Have i doomed my tank by putting in an emerald crab?

[dekonstruktr]

My bc29 has cycled and my LR has lots of fuzzy treats and diatoms on it so I decided to put in part of my CUC.. 5 little hermits, a Turbo snail, 2 Nassarius snails, a butterscotch Nassarius, and...

 

A little emerald crab. he seems to already be running the tank, and every time I look in he's in a different spot or cruising around the perimeter. I really like this little crab but every reef forum is full of nightmare tales about evil emerald crabs going on a wild killing spree leaving a trail of crabby destruction behind. There seems to be a split between skeptical crab owner with sweet crabs and crab haters who had to resort to tearing up their tanks trying to catch these green menaces and banish them to bad invert timeout.

 

Do I have anything to fear, or should I just wait to stock for a while until I see how this crab turns out?

[Daleo]

I love mine! My mom sees it carrying off a fish, and assumes that it killed the fish when the fish was probably dying and the crab was being "opportunistic"... Mine never nip at coral, but I am sure some emerald crabs do. Plus it helps if you feed them or leave food for them to eat.

[jbfrompa]

Mine shares a hole with my fire fish that hardly ever moves and I have had no problems. Just make sure it is well fed and you will have no problems.

[whitrose02]

My bc29 has cycled and my LR has lots of fuzzy treats and diatoms on it so I decided to put in part of my CUC.. 5 little hermits, a Turbo snail, 2 Narcissus snails, a butterscotch Narcissus, and...

 

A little emerald crab. he seems to already be running the tank, and every time I look in he's in a different spot or cruising around the perimeter. I really like this little crab but every reef forum is full of nightmare tales about evil emerald crabs going on a wild killing spree leaving a trail of crabby destruction behind. There seems to be a split between skeptical crab owner with sweet crabs and crab haters who had to resort to tearing up their tanks trying to catch these green menaces and banish them to bad invert timeout.

 

Do I have anything to fear, or should I just wait to stock for a while until I see how this crab turns out?

 

That's a lot to add all at once, particularly 5 red-legged right after cycling. You're clean-up crew needs to have things to clean to stay happy and healthy... Your emerald might be getting defensive because there isn't enough stuff for everyone. They are herbivores, so if you don't have any algae growing yet, they won't have any food. I haven't had luck with supplementing nori or anything with the emeralds.

 

Personally, I have 2 in my 40br and haven't had any problems.

[DC5]

Your mileage may vary. Some people have no issues, and some have nightmares. They are rumored to eat what they can catch.

 

However, sometimes people think they have purchased an Emerald, but they have really gotten a different crab that simply resembles one and those can be aggressive.

[ry05coupe]

I think it depends on the crab. I had two in my 40b. As soon as I put them in they both started going after my small clowns ad nipping at almost every softie and LPS in the tank. I would see the clowns with new nips in their fins every day. As soon as I put them on sump duty that stopped. I felt bad about 3mo later and threw them back in the tank. One went STRAIGHT to the hammer and started nibbline, the other got some GSP. They died in the sump.

 

Then again, a buddy of mie has had one for a good few months now and it hasn't touched anything in his tank at all, including his small clowns.

[Coastie]

^ Ya but I put him in my sump while I was gone just to be on the safe side.

 

I caught him nibbling on my GSP once and I scared him away from it. I usually put a small sheet of algae in my tank every now and again and he instantly went for it. He'd grab a large chunk after knocking the hermits and snails out of the way then run back to his cave and munch away.

[JoeyG40c]

Yeah it goes both ways. When I first set up my biocube I put two in and they were model citizens. Great cleaners and never bothered a thing. After about a year they both died. I recently added a new small one to combat some bubble algea and he is the devil. I caught him yesterday tearing chunks off of my favorite acan colony so I caught the little bastard and banished him. Personally I wont put them in again. I really like them and they add personality but if you have coral they are not worth it.

[Coastie]

I think the thing is, if you don't have enough algae to feed him make sure to toss some algae in there for him to eat.

 

If you were starving you'd eat whatever you could right?

[dekonstruktr]

I guess ill see how he works out. I am going to try to supplement his food if it seems that he is very hungry. Everything I got was freshly in the drip acc. tank at my LFS, I'm guessing nothing had been fed since they'd likely been in transport.

 

Is that really a lot at once? The cuc packages I've seen on reef cleaners and other sites are like 70 creatures for a 30 gallon! The hermits are really tiny, with shells the size of your thumbnail

[Doc Holiday]

Yes, those little buggers can go both ways. I've had problems and had no problems. The latest emerald crab started picking polyps off my purple stylophora. I caught him and placed him in QT for a while. When I returned him to the tank, I had much more alge for him to eat and he stays away from my SPS. I guess caution and observation is the best bet for these crabs.

[Coastie]

I guess ill see how he works out. I am going to try to supplement his food if it seems that he is very hungry. Everything I got was freshly in the drip acc. tank at my LFS, I'm guessing nothing had been fed since they'd likely been in transport.

 

Is that really a lot at once? The cuc packages I've seen on reef cleaners and other sites are like 70 creatures for a 30 gallon! The hermits are really tiny, with shells the size of your thumbnail

 

It' a clean up crew. The only reason that would be a lot is if your tank is sparkling clean.

[ry05coupe]

I think the thing is, if you don't have enough algae to feed him make sure to toss some algae in there for him to eat.

 

If you were starving you'd eat whatever you could right?

 

 

IDK man... my tank was like a forest of GHA got a good 3 months of it's life.

[dekonstruktr]

I tested the emerald by target feeding him a small square of nori with chopsticks and he totally went for it! He has eaten about half of it and is hanging in this little crevice with the rest of it.

 

One concern I have is this so called "butterscotch nassarius" my LFS sold me.. turns out to be a babylonia snail that is considered not really reef safe as they are predatory and eat other small inverts when there is not enough food. I dropped a little frozen brine shimp in by him and my other nasses and he popped out of the sand like a zombie and went for the food. I'm hoping if maybe I feed him and keep him fat he won't eat my other snails or hermits.

[Coastie]

Toss it in one of the back chambers of your biocube?

[bioload]

Your mileage may vary. Some people have no issues, and some have nightmares. They are rumored to eat what they can catch.

 

However, sometimes people think they have purchased an Emerald, but they have really gotten a different crab that simply resembles one and those can be aggressive.

 

First off, make sure you have Mithrax sculptus, like dcmix said other crabs may look similar but have different habits.Hopefully you got it from a reliable source. That being said, emeralds are primarily algae eaters of just about any kind....even valonia. IMO the best bubble algae controller in a small tank.However if the algae source is scarce they will turn to other things unless you feed them. I've personally witnessed one eating Seriatopora sp. polyps.I've also seen one eating a royal gramma which was perfectly healthy and eating before the lights went off( can't prove he actually caught it) The crabs are pretty easy to catch however, they are more prone to latch on to whatever they are on then try to run. Prying them loose is the hard part because they are surprisingly strong!Bottom line is I do keep 1 in each of my tanks but watch them closely.

[GokesReef]

Everything you do in this hobby dooms your tank. Even setting it up. Didn't you hear?

 

Seriously, though.. horror stories about everything. My tank has a six line and an emerald crab in it. I'm surprised the glass is still holding up!

[FishStrings]

IMO emerald crabs are just not a reef safe animal and better left in a live rock with just fish or a fuge. I know they enjoy eating gorgonians, some polyps and xenia, as well as zoas. They may be fine in larger setups though.

[Durbelethwen]

I would like to put in my two cent experience. I have an emerald crab that hitchhiked on my rock of turtle weed. I unfortunately did not see him until he had completely decimated my turtle weed. He has not bothered any of my other invertebrates and my Mom said that she saw a couple of my sexy shrimp dancing very close to where my emerald crab was eating algae and the crab did not care. My turtle grass came back, though when it had grown a fair amount the emerald crab also went back to the rock; I tried to chase him out, but I was unable to completely detour him and he ate the grass down to the rock again.

btw: I am thinking of taking the rock out of my tank and putting it in my one gallon and placing it under my Dad's seed propagation lamp until it has fully come back.

[reef-luva]

I don't like them in small reefs...they will eat anything and that means everything

if they feel the need.

Keeping them fed, tryin to stay ahead of their eating game is your best shot.

To me it' just not worth it, there are many "cute" alternatives for me...

[TinyGiant]

i have two huge ones in my 55 and just added 2 more smaller ones.. havent had any issues other than pushing a frag plug over here and there

[Northern Enlighted]

Everything you do in this hobby dooms your tank. Even setting it up. Didn't you hear?

 

Seriously, though.. horror stories about everything. My tank has a six line and an emerald crab in it. I'm surprised the glass is still holding up!

 

LMAO yea right! That's a good line man! Anyway to the poster, all these little critters for the most part live near each other on the reefs...BUT those reefs are huge, therefore pretty much ANYTHING in this trade has to be tried and true, thier arent really any facts into livestock behavior. When we take these critters who live maybe 1 species per square acre on a reef and stick 3 of them in a tank that 100gallons, you can see why they start to have problems or behave differently than in the wild. One thing works for someone while it doesnt for the other. You pretty much have to try and fail/try and succeed thing going there... Some dogs can live with cats, some cant....

 

My 2 cents, keep the crab happy by feeding it normally. If it starts eating your corals, yank it and send it packing. It's as simple as that man...

 

How hard would it be to judge a person by the things they do when they are 5 years old? When that same person is 35, things will be totally different. Why would it be different in reef livestock? Everything is different, the only way to see is to try it out...

[jokim]

I have heard all the horror stories on emerald crabs but i decided to get one anyway. he was one of the first cuc member i added since there was a lot of LHA growing everywhere. He has grown a lot in 2 weeks and almost cleaned out all of the LHA in the tank. he mostly hides and only aggression i have seen him was to a hermit crab walking next to him.

 

Now i was wondering what the little white particals in the tank and i see my hermit crabs munching on the little featherdusters that were on my rock.

[bioload]

Heres another horror story.....VERY funny except for the tragic death involved

 

 

http://www.3reef.com/forums/inverts/hermit...crab-85551.html

[dekonstruktr]

My emerald crab has been behaving thus far and has been a very good CUC member! I need to pick up some more nori for him because i left the bag out by mistake and my dog ate (!) but I see him picking at the rocks all the time and has not attacked anything to my knowledge. I have seen him futilely reaching his tiny claws at the fish but there is no way he can catch them.

 

His shell has a few white spots on it now but I am not sure if that means he hasn't been eating enough green algae or that he is beginning to molt. I tend to think it is the latter because he has been hiding out a lot more than before.

 

My only concern is that my firefish found a very vulnerable sleeping spot in a little cave behind the rocks on the ground. He might be easy prey there unfortunately.

 

Anyway, +1 in favor of emerald crabs so far!