Emerald Crab killed Wrasse?!

[Mattrg02]

I JUST caught my emerald crab eating my ruby longfin wrasse! The wrasse literally was swimming around and eating food just minutes ago. I walk up to see what this disturbance is going on and I see him with the fish, running around the bottom, eating the heck out of my fish.

This is the first that I’ve ever seen or heard of. I managed to catch him with my hands because he refused to let go of the fish. He’s now sulking in my sump. I can’t believe this. Just days ago he was pulling polyps off my new pc rainbow frag, should have known. Homicidal maniac isn’t happy with bubble algae nor mysis shrimp, he wants $$$$ fish and corals polyps.

What a jerk! Hope he enjoys life’s in the dark sump. Probably will mutate into some Hills have eyes, propper nutter, down there.

 

[tiggs]

I JUST caught my emerald crab eating my ruby longfin wrasse! The wrasse literally was swimming around and eating food just minutes ago. I walk up to see what this disturbance is going on and I see him with the fish, running around the bottom, eating the heck out of my fish.

This is the first that I’ve ever seen or heard of. I managed to catch him with my hands because he refused to let go of the fish. He’s now sulking in my sump. I can’t believe this. Just days ago he was pulling polyps off my new pc rainbow frag, should have known. Homicidal maniac isn’t happy with bubble algae nor mysis shrimp, he wants $$$$ fish and corals polyps.

What a jerk!

They can definitely be opportunistic eaters. For the most part, they're reef safe and won't eat any fish that are alive (although they will make quick work of dead ones), but I've heard of a few occasions where they've turned very predatory. It sucks that you landed an oddball!

 

[Mattrg02]

They can definitely be opportunistic eaters. For the most part, they're reef safe and won't eat any fish that are alive (although they will make quick work of dead ones), but I've heard of a few occasions where they've turned very predatory. It sucks that you landed an oddball!

He’s the largest that I’ve seen, definitely a male as well. Can’t believe that a $4 crab just took out a $40 fish! At least I was able to get him into the sump.

 

[jd371]

This is why I stuck to snails and shrimp for a CUC.

 

[Mattrg02]

I’ve had them in the past, not nearly as big as this guy, and they were females. I should have taken the dead body back to the LFS and let him see what his $4 crab cost me. That burns me up. At least he’s doing time in the sump. He can eat detritus for the rest of his life.

 

[chipmunkofdoom2]

How long have you had the wrasse? Did it go through a QT process and was it inspected for diseases? How healthy are the other fish in your tank?

It's pretty common for people to blame emerald crabs for killing fish because they see the crab eating the carcass. While it's not impossible for an emerald crab to catch and kill a fish, it's not the most likely explanation. Emerald crabs are relatively slow, about an inch wide at most and have flat claws designed for picking algae off rocks. They're not bobbit worms or mantis shrimp. While emeralds can catch and kill a fish, they're not predatory and they're not designed to do so from an evolutionary standpoint. It would be pretty difficult for an emerald crab to ambush and kill a healthy fish that's many times its size, even if the crab was hungry. Now if the fish was sick or suffering from some internal parasite that was not immediately apparent, then the emerald might have a better shot. But, I think these guys get a much worse reputation than they deserve.

If you did not see the emerald ambush and kill the wrasse, I would not blame the death on the crab.

 

[Mattrg02]

How long have you had the wrasse? Did it go through a QT process and was it inspected for diseases? How healthy are the other fish in your tank?

It's pretty common for people to blame emerald crabs for killing fish because they see the crab eating the carcass. While it's not impossible for an emerald crab to catch and kill a fish, it's not the most likely explanation. Emerald crabs are relatively slow, about an inch wide at most and have flat claws designed for picking algae off rocks. They're not bobbit worms or mantis shrimp. While emeralds can catch and kill a fish, they're not predatory and they're not designed to do so from an evolutionary standpoint. It would be pretty difficult for an emerald crab to ambush and kill a healthy fish that's many times its size, even if the crab was hungry. Now if the fish was sick or suffering from some internal parasite that was not immediately apparent, then the emerald might have a better shot. But, I think these guys get a much worse reputation than they deserve.

If you did not see the emerald ambush and kill the wrasse, I would not blame the death on the crab.

The fish would have had to have had a widow maker heart attack just as I sat down. He has was flying around the tank eating. I looked him over after I got him out and didn’t see any signs of disease.

He came from liveaquaria two weeks ago. The other fish are all healthy from what I can tell.

This crab is huge. He’s bigger than the wrasse and is very aggressive towards the other fish. He’ll reach out at them as they swim by, especially when I put food in the water. He’s not interested in the bubble algae that he was brought for, he wants coral polyps and mysis.

 

[Bayareareefer18]

The fish would have had to have had a widow maker heart attack just as I sat down. He has was flying around the tank eating. I looked him over after I got him out and didn’t see any signs of disease.

He came from liveaquaria two weeks ago. The other fish are all healthy from what I can tell.

This crab is huge. He’s bigger than the wrasse and is very aggressive towards the other fish. He’ll reach out at them as they swim by, especially when I put food in the water. He’s not interested in the bubble algae that he was brought for, he wants coral polyps and mysis.

Bigger than the wrasse? Now I wanna see a photo of this beast lol.

Sorry for the loss btw

 

[chipmunkofdoom2]

The fish would have had to have had a widow maker heart attack just as I sat down. He has was flying around the tank eating. I looked him over after I got him out and didn’t see any signs of disease.

He came from liveaquaria two weeks ago. The other fish are all healthy from what I can tell.

This crab is huge. He’s bigger than the wrasse and is very aggressive towards the other fish. He’ll reach out at them as they swim by, especially when I put food in the water. He’s not interested in the bubble algae that he was brought for, he wants coral polyps and mysis.

There are lots of things internally that could cause death that you would never see unless you opened the fish up and knew what to look for. Cyanide poisoning is a good example. Here's an interesting, perhaps applicable, excerpt from a ReefKeeping article:

Both the experimental and control group were observed to eat the day following the treatment. Additionally, there was no discernible difference in the external appearance of exposed versus unexposed fishes in this experiment. But, upon further examinations during necropsies, the cyanide exposed fish were shown to have intestinal and stomach damage that the untreated control group did not have; specifically, the exposed fish suffered from a sloughing of the inner gut lining (gastric mucosa). Additionally, in the anterior intestine, the mucosal folds had decreased in size. It is this damage that has led to the belief that cyanide caught fish may feed normally, but are incapable of digesting their food. They are, therefore, thought to slowly starve to death over time.

I don't mean to diagnose the fish with cyanide poisoning. But without performing a necropsy, it's impossible to say that the cause of death was the crab. Additionally, every emerald crab I've ever owned has been territorial when a fish has come near its burrow. Just being aggressive around feeding time or defending its territory does not make the emerald crab a killer.

If you're convinced that the crab killed the fish, there's likely not much I can do to convince you otherwise. However, as a matter of principle, I always reply to threads where aquarists claim an emerald crab killed a fish without actually witnessing it. It's possible, but it's just not that likely. In truth, you really didn't have the fish that long. It's entirely possible that it came with a pre-existing condition you didn't know about.

 

[Mattrg02]

There are lots of things internally that could cause death that you would never see unless you opened the fish up and knew what to look for. Cyanide poisoning is a good example. Here's an interesting, perhaps applicable, excerpt from a ReefKeeping article:



I don't mean to diagnose the fish with cyanide poisoning. But without performing a necropsy, it's impossible to say that the cause of death was the crab. Additionally, every emerald crab I've ever owned has been territorial when a fish has come near its burrow. Just being aggressive around feeding time or defending its territory does not make the emerald crab a killer.

If you're convinced that the crab killed the fish, there's likely not much I can do to convince you otherwise. However, as a matter of principle, I always reply to threads where aquarists claim an emerald crab killed a fish without actually witnessing it. It's possible, but it's just not that likely. In truth, you really didn't have the fish that long. It's entirely possible that it came with a pre-existing condition you didn't know about.

True on all points, but the only evidence available is that a seemingly healthy, and eating, fish was dead moments later, found in the claws of a crab that has a bad reputation in my tank. Sometimes, that’s the only thing one can go on.

He’s in the sump, sitting on a rock, looking up at me. I’ll try to snap a pic of this bad hombre later.

 

[kashman100]

I had an emerald crab that was clearly trying to catch fish. It would try to grab it every time it got close. So I would say its possible

 

[shred5]

Mine was eating cleaner shrimp and sexy shrimp.. I was loosing them and could not figure out how till I saw him grab a cleaner shrimp.
They can blend in real well or sit in a hole and are fast with their claws so there is no doubt even if rare they can catch a fish.

 

[Dilan Patel]

That is a massive crab lol. I would be scared to own it thinkng it would eat me while i was working in the tank. Sorry for the loss. As someone has already stated is it possible that the fish was weak? The crab I believe is not that fast so the fish would have had to been considerably weak for the crab to catch it.

 

[Mattrg02]

That is a massive crab lol. I would be scared to own it thinkng it would eat me while i was working in the tank. Sorry for the loss. As someone has already stated is it possible that the fish was weak? The crab I believe is not that fast so the fish would have had to been considerably weak for the crab to catch it.

Oh these guys are fast alright. Ever try to catch one? When I saw him going to town on my pc rainbow, I tried to get him out then and there.

The fish didn’t act weak. He was pretty quick in the water. Also a very aggressive eater, competing with a Midas Blenny many times his size, as well as a homicidal clown fish.

Edit: Do emeralds eat detritus? If not, I’ll drop the bubble algae, that he was SUPPOSED to be eating, in the sump for him.

 

[Dilan Patel]

wow i have no idea then. if u want to get rid of bubnle algae i reccomend a rabbitfish if u got the space. very reef safe in my experience and docile.

 

[shred5]

Oh these guys are fast alright. Ever try to catch one? When I saw him going to town on my pc rainbow, I tried to get him out then and there.

The fish didn’t act weak. He was pretty quick in the water. Also a very aggressive eater, competing with a Midas Blenny many times his size, as well as a homicidal clown fish.

Edit: Do emeralds eat detritus? If not, I’ll drop the bubble algae, that he was SUPPOSED to be eating, in the sump for him.

They will eat pretty much anything if they can.. Pellets fish food will work just fine, even a sheet of nori. On geared towards herbivorous would be best.

 

[Adele]

I love Emeralds, until a new one I had in my DT took out a two head Duncan. Thought for sure there was something wrong with the Duncan and he was simply eating the necrotic tissue. Enter two more Duncan's a few months later. Came home from work one day and there he was at the Duncan buffet tearing away the skin. He's trippin in the Fuge with rose colored lighting.

 

[choss]

I'd like to see a picture of the crab. Perhaps it was sold s an emerald but is really another species?

 

[Mattrg02]

I'd like to see a picture of the crab. Perhaps it was sold s an emerald but is really another species?

He’s definitely an emerald crab. Not very green though. He’s got the claws of an emerald, but no appetite for bubble algae. Here’s a picture of him in solitary. Hard to see him very well, but he’s there in top of the rock.

 

[choss]

Really hard to tell from the pic but he looks big