Emerald Crab, Are they AGGRESSIVE

[zues2006]

Hello,

I've had an Emerald Crab for about 3 months now. I think he's a great addition to my tank. I've got a 30 gallon now. I've had a few different fish in the tank with him over time. A clown fish, a damsel or two, and a watchman goby. There's never been an issue with him and the fish in the tank. But, he's almost doubled in size since I've gotten him. Just this weekend, I've added a Coral Beauty to my tank. Within 30 minutes of letting the Coral Beauty free in the tank, the Emerald Crab took some swipes at the Coral Beauty and it looks like the Crab did a little damage/scratched/wounded the Coral Beauty. Have any of you guys known Emerald Crabs to be aggessive towards fish? I love the Crab, but if he's going to attack my fish, I'd have to part with the Crab. I've got lots of live rock for the Crab, and maybe I could set up my rock better, so that the Coral Beauty wouldn't swim so much through the rock (the crabs domain). Let me know your experiences with emerald crabs.

thanks,

[drillsar]

When emerald crabs get adult size yes they can be a problem, I personally dont like them

[gws76]

I've got an emerald crab that does the same thing. Crabs are opportunistic. When I first added mushroom coral and green star polyps, the crab taste tested them a few times. I was worried at first, but after a few days he settled down. So far anything I add to the tank the crab is curious about it for a little while. I'm not sure if rearranging the rock will help, but you might try it. If it works let me know please.

[stingythingy45]

The crab was just protecting it's turf.
And I have a very large one also and never had a problem.
The CB was new and didn't know where the crabs territory was.
That will change....

[zues2006]

I was thinking of rearraging my rocks anyway, so we'll see if that helps things at all. I'd hate to lose my fish over a $10 crab

[dja1980]

Do you need the crab? In other words, do you have an algae issue you are trying to deal with? Personally, I don't add crabs of any type to my system unless they are to serve a purpose. As gws76 stated, they are opportunistic feeders, and from what I've heard, can be hit or miss as far as problems are concerned.

[zues2006]

<a href=showthread.php?s=&postid=11877841#post11877841 target=_blank>Originally posted</a> by dja1980
Do you need the crab? In other words, do you have an algae issue you are trying to deal with? Personally, I don't add crabs of any type to my system unless they are to serve a purpose. As gws76 stated, they are opportunistic feeders, and from what I've heard, can be hit or miss as far as problems are concerned.

I don't have an algae problem, that I can see. I do enjoy having him in my tank though, he is a cool critter, that is untill he keeps attacking my fish. I'm going to keep a real close eye on the situation for a few days and see what happens. I was going to rearrange my rocks anyway, so I'll just do that sooner, rather than later (probably tonight). Crafy had given me some suggestions on how to orientate my rocks better. I'll try that and see what happens. If the crab wounds the fish again though, I'll put the crab in the other tank I've got untill I can get rid of him. We'll see what happens.

[BigScott]

i put mine in my sump.. he kept eating my snails..

[craftytony]

Scott, you SHOULD be allright, but as has been said, they are oppurtunistic and I don't like having them unless they are living in an acro. If you need to get rid of it, give it to beefy, his tank is full of crabs ;)

Have you moved your rock around yet?

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[jubjub]

.......mine has been a model citizen..personally i like them they just look cool when they are visible...

[jon99]

Same here, so far so good.

[hootie51]

I had one that attacked and killed a royal gramma shortly after introducing it and ate all my snails. That was the last crab I have ever put in my tank. I'm a member of the crabs are evil club!

[jon99]

Same here, so far so good.

[zues2006]

Sounds like more people say that their crabs are not a problem, but after looking closer, everyone that said the crab was not a problem had a 40 gallon or bigger tank. I wonder if the size of the tank makes a difference. The crab might think a high percentage of the tank is his territory, and since the CB has less space to swim through, he is forced to swim through the crabs territory. I think I'll rearrange the rocks tonight and see what happens.

[DragonRage]

My emerald only touches the algea in my tank and its a 28, he's almost as big as my clown

[sruiz]

I had mine in my tank for about a year and he was good(he was 2.5 inches wide when i got him), recently i saw him eating my zoos. Sooner or later yours will do the same, but they usually only come out at night so that might be the reason many people think they are doing ok in their tank. Throw him in the sump.

[craftytony]

(he doesn't have a sump) ;)

[blumarlin]

I have a coral beauty that had wounds, nicks on her a few weeks ago. Freaked out thinking she was sick. After lots of info here, we thought maybe my clarki nipped @ her or maybe the frogspawn stung her. She has healed, although, I noticed a fresh nick on her side this a.m.
I have spent alot more time watching my tank & the clarki & frogspawn are not the problem.
I have a sally lightfoot (that I have seen grab @ my yellow tang, but only when she swims by her territory). I also have a mystery crab that hitch hiked in on a piece of live rock. He is purple w/ one HUGE claw that almost looks like a stone crab
::eek2: I have a feeling he is the culprit. Have tried to catch him, but he is way too smart :mad2:
I have heard as long as the crabs are well fed, there is usually not a problem. But their appitites get bigger as do they.
In my opinion, crabs in a reef tank are not a good thing. Do some research on the net & you will see.
Best of luck!

[craftytony]

I'm glad my sally is gone.....it used to go after all my fish!

[stingythingy45]

<a href=showthread.php?s=&postid=11885818#post11885818 target=_blank>Originally posted</a> by blumarlin
I have a coral beauty that had wounds, nicks on her a few weeks ago. Freaked out thinking she was sick. After lots of info here, we thought maybe my clarki nipped @ her or maybe the frogspawn stung her. She has healed, although, I noticed a fresh nick on her side this a.m.
I have spent alot more time watching my tank & the clarki & frogspawn are not the problem.
I have a sally lightfoot (that I have seen grab @ my yellow tang, but only when she swims by her territory). I also have a mystery crab that hitch hiked in on a piece of live rock. He is purple w/ one HUGE claw that almost looks like a stone crab
::eek2: I have a feeling he is the culprit. Have tried to catch him, but he is way too smart :mad2:
I have heard as long as the crabs are well fed, there is usually not a problem. But their appitites get bigger as do they.
In my opinion, crabs in a reef tank are not a good thing. Do some research on the net & you will see.
Best of luck!

So you let a hitchhicker crab ruin your day,but all crabs in a Reef tank is bad news?
Me thinks you need to catch the hitchhiker crab.
They do have traps for that sort of critter.

[blumarlin]

I have bought a trap & even tried the bottle trick several times. The only things I have caught is a couple of red legged hermits. Oh, & once I caught my baby cleaner shrimp. Boy, was he glad to get out of there, never went there again:D.
So, yeah, crabs in my tank kind of put a damper on my day, especially when I see my fish has been attacked one than once.
I really cant say for sure its the crabs, but I would put my money on it.

[scrmbld33]

i had 2 in 90, they never bothered anything that i know of,

[stingythingy45]

You need a little lobster type trap with some really stinky bait(silverside guts).
Inverted top cut off a 12 liter plastic soda bottle.
Set it at night near the crabs hidy hole and you'll have him in the morning.

[blumarlin]

I read a post on here once about a guy who watched helpless as a sally grabbed his yellow tang & pulled it under a rock never to be seen again. He had a very large tank w/ many corals & live rock & couldnt get to it.
Wet Web Media also has similar stories.
I added my sally as part of a cleaner package w/out doing reshearch. After the fact, I did reshearch & 95% of what I found out is they ar NOT reef safe.
I guess some are better than others, as all fish dont have the same personalities ie: one clown is a model citizen & another is a holy terror:)

[blumarlin]

You need a little lobster type trap with some really stinky bait(silverside guts).
Inverted top cut off a 12 liter plastic soda bottle.
Set it at night near the crabs hidy hole and you'll have him in the morning.

I have a lobster type trab, but I have never tried that. Thanks for the advice! I will give it a try tonight.

[tifluvsu80]

I have 2 in a 30gal. My bigger one just molted so he is really big. WHen I first got my 2nd emerald he and my Sally go into a fight and they each lost a claw. THe only other think I noticed is that they clip my plants off my rock.

[stingythingy45]

Hey,I'm from New England,we know how to catch our crabs....um....I mean crustations.

[dja1980]

<a href=showthread.php?s=&postid=11886344#post11886344 target=_blank>Originally posted</a> by blumarlin
I read a post on here once about a guy who watched helpless as a sally grabbed his yellow tang & pulled it under a rock never to be seen again. He had a very large tank w/ many corals & live rock & couldnt get to it.
Wet Web Media also has similar stories.
I added my sally as part of a cleaner package w/out doing reshearch. After the fact, I did reshearch & 95% of what I found out is they ar NOT reef safe.
I guess some are better than others, as all fish dont have the same personalities ie: one clown is a model citizen & another is a holy terror:)
Yeah, those things creep me out!

[SteveOhio]

I bought a small glass salt shaker and removed the lid and leaned up against a rock area near where the crab lived and put food at the bottom of the salt shaker. When I woke up the next morning, he was laying at the bottom. He is now in my sump. I presume and blame him for killing three of my fish. Since I put him there, I have added two more fish with no problem so I believe he was the culprit.

[gprdypoo04]

I've got an emerald in my 40 gallon and no problems with other corals, fish or other invertebrates. I was a little concerned when he was hanging around my hammer coral but he seems to hide out in it. I do feed him seaweed quite often though.

[Sk8r]

They will nip fish fins. They are a predator. Slow-moving or ground-bound fishes are at risk. Coral banded shrimp, same deal. Sally lightfoots have another problem: they grow to the size of a dinnerplate.

[tomreefer]

All crabs will eat anything they want when hungry and why I don't put them in.