possible predator crab in my tank!!

[jason7504]

i noticed this good sized hitchhiker crab out in the open about a month ago and haven't seen it since. I see that it now has a lil cave in the sand under a rock towards the front. It look kinda brown and fuzzy with some black on half of its claw. It seems like a pretty big crab and its claws are good sized. I have noticed 2 of my pipefish all of a sudden disappearing and i thought maybe something like a crab was eating them. Well i looked in the cave and saw him eating part of my pipefish sad.gif i dont know if he scavenged it or killed it. I haven't noticed any of my snails missing but he's probably been nourished with my 2 pipes :/

 

I hope he's not a rock crab or some kind of predatory crab. what do you guys think? could i trap him?

[jgf86123]

id get him out of there asap, black claws is bad joojoo mange

[jason7504]

well there not all black. it looks like half are a faint black and the rest looks to be fuzzy brown..how hard do you think it would be to trap him?

 

joojoo mange?

[talkalot82]

I had that crab once but he never went after my corals or fish. Never did find out what he is. still there. but like I said I dont have pipe fish that are easy prey.. so maybe not a good reefer crab with pipe fish. or maybe your pipe fish was dead already watch the tank for a day or two if it was me. no use killing something if you dont have to cause crabs are scavengers.

 

 

But I have issues killing living creatures. I'm so bad i bury all my dead fish and say kind words. even gold fish and my bettas

[Saltfinsax]

I would try and catch one just to gett a better look. Try and look at night with just a little light or red light to see what there doing. Both my hitchhiker crabs have cups on the ends of there claws and both have black and white claws. Both seem to just scrap the rocks as far as I have seen.

pic of the big guy.

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[andy]

The list of good-guy crabs is a lot shorter than the bad-guy list. To make matters worse, many of the "good-guys" will do bad things when you aren't looking.

 

One general rule of thumb is that "hairy" crabs are bad-guys. If it was my tank, I'd get it out of there asap. A one-liter pop bottle with the top end cut off, leaned up at a sharp angle against some rock and baited with some fresh shrimp should work. Crabs check in, but can't check out.

 

Once caught, toss it in the sump or try and sell it to your local Red Lobster.

[Lowman]

when in doubt about things with claws, the best thing to do is sentence them to exile in the refugium or sump or make them trigger food.

[Mikep503]

From what I understand there isn't a fuzzy crab anywhere on the good list! Good luck getting him out. took me two years to catch one of mine. A drinking glass tipped against a rock with food in the bottom works well. To slick for them to climb back out.

[ThePremiumAquarium]

I would try and catch one just to gett a better look. Try and look at night with just a little light or red light to see what there doing. Both my hitchhiker crabs have cups on the ends of there claws and both have black and white claws. Both seem to just scrap the rocks as far as I have seen.

 

From what I can tell, your two crabs look like a variety of mithrax crab. I have had many just like these over the years that have been mostly a benefit to the tank.

 

 

Jason, it definatley sounds like you have a gorilla crab in your tank. I would recommend using Bob's suggestion on these guys. I had one that grew from thumb nail sized to over palm sized and it ate all sorts of star polyps, occasional zoas, and I would occasionally find fish remanents near or in his cave though who knows whether it he actually killed the fish or if he was just cleaning up the mess.