What are your thoughts on these guys? Reef Safe? I have 2 or 3 emerald crabs I've had for about a year, and they are getting mighty big. Anyone had one catch a fish or attack? I'm thinking maybe I should consider putting them in the sump.
Emerald Crabs
- Thread starter Kigs!
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I've never really had these in the tank but I'm considering one or two to take care of a little bubble algae issue... I also plan on taking them out after they get a little bigger just for precautionary measures... I would just try to trade them at you LFS for smaller ones... good luck..
R
reef-nut
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Ever see them eat coral of any kind?
I've heard of them being a problem when they get bigger...
Russellaqua
Coral Junkie
Emerald crabs are one of the few harmless crabs out there. No matter how big they get they only seem interested in algae, and are one of the few things that will eat bubble algae. I've kept some very large ones that never bothered any coral or fish, just algae.
Who Dah?
Exoticfrags.us
Man, I hate to post the opposite of what Russell just did... But I pulled out 3 last week out of my work tank because they did just that! One caught a twin-spot goby and were eating Zoanthids out of the base. It would pull out chunks of the mat and the guts of the polyps from beneath (As opposed to the skirts and top). I was so mad that I got them out before taking a picture. Ugh.
At any rate, I got them very small, like the size of a dime and the one doing the damage had grown to over the size of a quarter. I pulled out all three.
I fed the tank quite a bit, but perhaps it was for lack of other food sources. I tell ya, they were my favorite critters in the tank and other then coraline, there was not a spec of algae in there that they didn't consume. (Further enforcing the lack of other food source theory?)
I would have them again - but only very small and I would pull them out after they cleaned up the tank and before they got large.
So - take it for what you will, but that's my experience!
At any rate, I got them very small, like the size of a dime and the one doing the damage had grown to over the size of a quarter. I pulled out all three.
I fed the tank quite a bit, but perhaps it was for lack of other food sources. I tell ya, they were my favorite critters in the tank and other then coraline, there was not a spec of algae in there that they didn't consume. (Further enforcing the lack of other food source theory?)
I would have them again - but only very small and I would pull them out after they cleaned up the tank and before they got large.
So - take it for what you will, but that's my experience!
THE BEAUT
Luv Golf
I have 5 in my tank, never had and issue. I love them, they keep the rock nice and clean. Every now and then they will walk over you corals looking for algae feeling their way around, but yet to see one take a chunk out of a coral. In all the years never had one catch a fish..
I love these guys also, I have 3 quarter sized emeralds in the tank and they definitely handle the algae. they have been in the tank for over a year. I see
them pull algae off the disks at the base of zoas, but never crunch or maul
any coral. But, I would pull them out in a minute if I saw them eating or shredding any coral.
them pull algae off the disks at the base of zoas, but never crunch or maul
any coral. But, I would pull them out in a minute if I saw them eating or shredding any coral.
Russellaqua
Coral Junkie
I'd definitely say if they're going after fish and corals they're lacking a food source. I once had a colony of zoos with lots of hair algae growing inbetween the polyps. The crabs would carefully put their claws in and pull out only the algae. I've seen them fight each other, but never seriously, and they've always left my purple reef lobster alone.
Well, I've taken heat for saying this before, so here goes. Personally, I would never ever trust an Emerald Crab or a Sally Lightfoot in a tank full of zoanthids and Playthoas. Both are continuous and voracious eaters. I have seen and caught both doing just that, munching on my polyps. I firmly believe that Emeralds are highly unpredictable. They may walk by your poylps for years and never touch them, but one day, I can assure you they will. Emeralds are herbivores until their shell reaches the diameter of quarter. Once they mature beyond this size, it's like russian roulette and they will become omnivores from my personal observation and anectdotal reports. There are countless threads on another sight of them eating/consuming zoanthids. I will go a step further and say that no flat crab, as I call them, is considered reef safe around zoanthid and should never be trusted. I have caught 6 adult crabs, not emeralds, in my tank and I have devised a way to remove each of them. If I had a small system with a few inexpensive zoas, I would leave them.
A. Calfo has even stated in his book, "As a rule, most crabs should be considered unpredictable to dangerous, as few are truly herbivores. Even the "safe" crabs like the algae grazing Mithrax species and seeral of the sand stirring hermits have occasionally been observed eating or attacking other reef denizens. The truth of the matter is that most crabs are truly omnivores and opportunistically predatory."
No offense, but whenever a see a speck of bubble algae, I rolled it off the rock. But I will never ever trust an emerald crab or any other like crab other than a clean up crew in my tank that's loaded with zoanthids and playthoas. Just my 2 pennies.
Mucho Reef
A. Calfo has even stated in his book, "As a rule, most crabs should be considered unpredictable to dangerous, as few are truly herbivores. Even the "safe" crabs like the algae grazing Mithrax species and seeral of the sand stirring hermits have occasionally been observed eating or attacking other reef denizens. The truth of the matter is that most crabs are truly omnivores and opportunistically predatory."
No offense, but whenever a see a speck of bubble algae, I rolled it off the rock. But I will never ever trust an emerald crab or any other like crab other than a clean up crew in my tank that's loaded with zoanthids and playthoas. Just my 2 pennies.
Mucho Reef
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revhtree
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Different strokes for different folks, but I tend to agree with you Mucho. They scare me and now they rank right up there with tangs! Yes all tangs! I just got rid of a powder blue and a salfin for coral nipping! Took out 2 of my Armageddons polyps and tore some acans up as well. I watched them eat it!
Russellaqua
Coral Junkie
It is true that no Mithrax crab can be considered 100% reef-safe. Nearly all crabs are detrimental to the reef life we like in our tanks. The only crabs I trust 100% are Trapeziid acro crabs, as these clean and improve the health of their acro host. They'll even take up residence in Seriatopora sp. and Pocillopora sp. corals. Emeralds are a great way to remove algae that we can't get to, but it is a cost/risk balance. If they start destroying things they should be removed (but not killed), and if a tank is watched each day the damage a crab can do is small compared to the job they perform. In the end all animals are individuals with their own personalities and tendencies. Some may never touch a coral, others will love them.
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True, true!
I should've taken them out sooner... I came home today and noticed that my female Rhomboid was missing, only to find her behind the rocks being eaten by the Emerald Crab. 
I have no way of proving that the crab killed her, but seeing that the Rhomboid was healthy for almost a year and nothing changed in the system recently....I'm going to play it safe and transfer the crabs to my sump. I knew I shouldn't have trusted them after they got big enough to be able to start lifting 2'' frag discs searching for food...
I have no way of proving that the crab killed her, but seeing that the Rhomboid was healthy for almost a year and nothing changed in the system recently....I'm going to play it safe and transfer the crabs to my sump. I knew I shouldn't have trusted them after they got big enough to be able to start lifting 2'' frag discs searching for food...
My experiance is similar to others. When my emeralds were small they did a great job but as they grew they would knock frags over and I witnessed them ripping flesh from acans trying to get to the mysis shrimp the acan was trying to eat. But again this only started when they were over quarter size. I have also seen sally lightfoots going after small fish - not in my tank but others locally. I hate it because I like the crabs for all the good - but I don't want the hassle of possibly tearing my rock work apart to catch them either.
Big Chippa
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In my mystery alea post I mentioned that I tryed putting in 4 emerald crabs to eat random bubble algea, well one has since started to eat small pieces of some of my acans off? I always thought they were harmless as well. I would not have belived it untill Isaw it with my 2 eyes.
I'd like to ask a question as it applies to these crabs. I agree with what most of you are saying and they won't be staying in my system long term. However, I just added 5 to remove some bubble algea.
You hear everyone say don't pop bubble algea it releases the spores. Well i watched these guys eat it for about an hour last night and they definetely without a doubt bust every one they eat. They grabbed the ones they could(larger ones to big for there pincher go uneaten), smashed it flat, ripped the shell off the rock then ate it. I saw 3 of the 5 all doing the same exact thing.
So why now would I not just start popping them myself too? I have my thoughts but will wait to see what others suggest.
Brandon
You hear everyone say don't pop bubble algea it releases the spores. Well i watched these guys eat it for about an hour last night and they definetely without a doubt bust every one they eat. They grabbed the ones they could(larger ones to big for there pincher go uneaten), smashed it flat, ripped the shell off the rock then ate it. I saw 3 of the 5 all doing the same exact thing.
So why now would I not just start popping them myself too? I have my thoughts but will wait to see what others suggest.
Brandon
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