Killer Emerald Crab?

[heuerfan]

I have about 6 emerald crabs in my 72 gallon tank that i have had for a year now and they never harmed anything. About a month ago i gave a big emerald crab to my friend to put in his 15 gallon tank. The emerald crab was about 3" when both claws opened up wide.

Last week the crab killed an expensive 4" wrasses, could not believe it told him maybe the wrasse injured itself and the crab took advantage. Today, the crab killed another wrasse that was 3.5".

Anyone experience emerald crabs to be fish killers? My emeralds are constantly feeding on the extra food i feed the tank, perhaps his emerald crab was starving and couldn't resist?

Thanks for your comments,
Steven

 

[zemuron114]

not me.. but i never keep crabs unless they are hermits or maybe acro crabs or anemone crabs...

 

[MarvinsReef]

only kept hermits with the fairies and flashers..

man, that was a pretty expensive loss...

 

[Sk8r]

It has been suspected in this forum before this. Crabs will take advantage of a food source if it is digestible for them, and sleeping fish might look like one, if the crab is large enough.

 

[kjbudsberg]

Crabs are opportinistic regardless of species. As grizzly as it is, I enjoy watching them work on a nearly dead snail...after all, it saves me from ahving to dig the foul mess out of there! Anyway, I think I have read about green crabs, sold as emerald crabs, that take a posture after lights-out with the body held very high, and when a fish swims underneath, it tries to make a kill.

 

[heuerfan]

<a href=showthread.php?s=&postid=7943418#post7943418 target=_blank>Originally posted</a> by MarvinsReef
only kept hermits with the fairies and flashers..

man, that was a pretty expensive loss...

Guess i've been lucky. I find it hard to believe that an emerald crab can catch a healthy wrasse but i guess you never know.

I've never seen my emeralds take a swipe at any fish, just see them flare with their claws out open wide. Even if it were to take a swipe at the wrasse the wrasse would be much faster. I know that emeralds are opportunistic crabs but i don't think they were made to kill fish........

Now i have to decide if i'm going to take all my emeralds out....

 

[DonavonsReef]

I doub't that crab killed anything. How many fish does this guy have in his tank? I have 3 emerald crabs in my 18 gallon reef they might do some clumsy stuff like knock over coral or pluck food out of a corals mouth but catch and kill a fish I doubt it. I have a mandarine, cherub angle, & a mystery wrasse 3 years no problems. I think your buddys figh are kicking the bucket & the crabs cleaning up the mess.

 

[DonavonsReef]

Not to mention these crabs find there food by sent & most wrasses sleep in a mucus cacoon that covers there sent when they sleep. I think your buddies water quality might be the problem. It's always easier to point the finger at the guy with the smoking gun.

 

[heuerfan]

DonavonsReef- i'm thinking the same also. 15 gallon tank with 15 lbs of live rock and a remora skimmer. Tank setup for almost 3 months. He had a 4" lineatus and a 3.5" flame wrasses and the one emerald crab........

Maybe water quality, but wouldn't that affect the crab?

 

[DonavonsReef]

In a 15 gallon tank with 15 lbs of live rock the rock displaces alot of water. Depending on the density of the rock he might only have 8-9 gallons of water or less. The tank is a new set up only 3 months old those two fish are decent size & would put out a suficent amount of waste. I don't know his feeding habits or how often he feeds the fish but in that small volume of water changes happen very fast. The water would affect the crab but the fish would be first to go & without the fish producing waste the bio-load would stable out. This is just an example of what might be happening. I would go out on a limb & say it's not the crab.

 

[heuerfan]

Thanks Donavon, that makes alot of sense.