Predator emerald crab!

[Retired_AF]

I have an emerald crab that has gone predator on me. He has killed my Caribbean Pygmy Angel and my Sunrise Dottyback is missing. I saw both last night swimming energetically and I saw the angel this morning. Tonight I fed the fish and immediately missed both of them. Looking around I found a crab behind a rock with its shell broken and the biggest crab was in the recess the angel usually hid in munching away on one of my favorite fish!

I dont know why he has suddenly started going after the fish but I have seen him grabbing at one that was near a piece of food.

I put 2 traps in and caught 1 in less than 30 minutes. I think I have 2 more (1 for sure that is still eating my angelfish) in the tank. He is hidden under a bunch of rocks and I cant get him without disassembling the tank rockwork.

Hopefully I will have them shortly.

 

[Jeremy S.]

Are you sure he killed the fish or did the fish die and he's cleaning up?

How long have you had the crabs and have you checked your water?

 

[LaWoWee]

Emerald crabs supposedly become aggressive as they get bigger/older. I got rid of mine after i caught it eating my birdsnest on consecutive nights. I dont really consider them reef safe anymore.

 

[Schism]

Emeralds are opportunistic feeders, but i highly doubt an emerald crab caught and killed 2 healthy fish. Either they died and the emerald was cleaning up or they where on there last leg and the crab took advantage but im leaning toward the first scenario.

Emeralds are known to pick at coral especially polyps but catching and killing a healthy fish is a whole other story.

 

[User Name]

Maybe a dumb question. But are you sure these are emerald crabs? I have seen other reefers think they have an emerald when it really wasn't. A picture might help.

 

[Jeremy S.]

Here's a picture of mine for reference.

 

[ocgirl]

My emerald crab attacked and killed my tang last night right when I watching in the dark. Tang was very healthy and active. He also tried go after my clown when he is sleeping on the sand bed. Had to take him back to LFS. He was always eating and I target fed him to make sure.

 

[ocminpin]

My emerald crab attacked and killed my tang last night right when I watching in the dark. Tang was very healthy and active. He also tried go after my clown when he is sleeping on the sand bed. Had to take him back to LFS. He was always eating and I target fed him to make sure.

:-( was so hard to watch the poor little tang... I'm sorry Dory

 

[Retired_AF]

Are you sure he killed the fish or did the fish die and he's cleaning up?

How long have you had the crabs and have you checked your water?

The fish were healthy and active yesterday, swimming and eating as they always have. I kept close watch on tham as they were my favorite fish. It IS possible they had something I couldnt see but all the others seem healthy and active and are eating well. I did a full battery of tests on the water yesterday and all the parameters were normal. pH is a little lower than usual but still in acceptable range. This crab has been in the tank over 6 months and his back shell is about the size of a quarter. His claws are about 1/4 inch thick.

Emerald crabs supposedly become aggressive as they get bigger/older. I got rid of mine after i caught it eating my birdsnest on consecutive nights. I dont really consider them reef safe anymore.

Interesting. My birdsnest has been losing polyps too......

Maybe a dumb question. But are you sure these are emerald crabs? I have seen other reefers think they have an emerald when it really wasn't. A picture might help.

Yep, I'm positive. It looks exactly like the pic Jeremy has posted.

Here's a picture of mine for reference.

Thanks Jeremy. Mine looks exactly like this.

I have been researching since I posted. I have found several posts on other forums where emeralds have started killing fish that rest in the caves or overhangs. Both of my fish did exactly that. Apparently the crab would trap the fish in its hiding place and kill it. This seems logical and that is exactly where I found him with my angelfish.

This crab was the cause of my having to remove the dragon algae from my tank that I bought last month. He was shredding and eating it.

When I catch them, into the sump they go..... Then I can put my dragon algae back.

 

[Jeremy S.]

Sucks to hear it was the little fella! I hope you catch him before more fatalities occur. He'll still live a nice life in the sump my Mantis shrimp loves my sump.

 

[Retired_AF]

I've caught 2 of them, neither of which are the culprit. it's just a matter of time before I get the bad boy.

All the other fish are doing fine. I checked them closely and dont see anything unusual. no spots, no flukes, no injured areas.