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  1. #1
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    Id this crab please!

    Hello.. Had this crab since I bought my first batch of liverock about 7-8 months ago. It's a hitch-hiker. It has tripled in size in that time (It's body is now about the size of a toonie. It used to be a whitsh-tan color and is now a very dark black and tan.

    Reef-Friend or Foe?

    I noticed Bonaqua posted a similar looking crab recently --> http://aquariacanada.com/forums/show...&threadid=7530

    Mine looks similar but not exactly the same. Mine looks like an emerald crab with long arms and big blunt white-tipped claws but very dark. The white claw tips are shaped like little spoons. I've been trying to get a picture for a long time but its hard since it seems very timid and tends to hide in the rocks all day. Any movement outside the tank at all will cause him to instantly dissapear into the rock. It eats detritus and coraline that I have seen anyway.

    Here are some pics!
    Thanks

  2. #2
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    Pic 2

    PIC 2

  3. #3
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    it doesn't look hairy at all has it touched your corals???

  4. #4
    Moderator Krugar's Avatar
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    I had 5 that looked like that. They also had an appetite for leather coral.

    I found out though that there are 10s of thousands of crabs that generally look like that & nobody knows all of them.

    If he's behaving he's likely more trouble to get out than it's worth. If not you might have to trap him. I ended up splitting live rock with a screwdriver to get some of these buggers out & even after than I had to sacrifice about a pound of rock to a week long RO bath to get them all.

    Any softies in the tank?

    Cheers!
    There is nothing so permanent as a temporary measure.

  5. #5
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    It's legs are a little hairy... can't really see that in the pic.

    I haven't seen it picking on any corals. I'll keep an eye on it though in case. It's going to be hard to get him out of there if it comes to that..

    Thanks

  6. #6
    Senior Member kjasjg's Avatar
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    there are so many types of crabs that come from live rock I've read somewhere (can't remember where) that a great many from the live rock are related to the mithrax crabs (emerald crabs). It is important to look at their claws though. Generally if it is shaped like the one in your picture (only the tips of the claws touch when closed) it is generally meant for scraping algea and other "gunk" off of rock. If the claws are shaped more like scissors then it is either used for hunting or defense.

    Jer
    Its the early bird that gets the worm, but its the second mouse that gets the cheese.

  7. #7
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    kjasjg,
    Yeah I'm inclined to agree with you about the claw shape. I've only ever seen it eat algea (mostly coraline) and detritus. And the fact that it's so neverous about any motion outside the tank leads me to believe he's very timid and hopfully be ok in the reef tank. I'll keep an eye on him though just in case.. It would be a shame to have to banish him to the sump (he's really cool to watch). But if I have to I will..


    Cheers!

  8. #8
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    IMO, keep it in the main tank. As you have mentioned, the spoon shaped claws are indicative of it being an algae eater and a good part of a cleanup crew. Yes, it will also eat coralline so some people still might not like it. It' won't be able to eat enough of it to make it diminish though. There are many varieties of crabs in the Mithrax (common Emerald crab) family, and the color of yours is also often available, although not nearly as much as the olive green variety.

  9. #9
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    Thanks Toutouche... I'll keep in the main tank and keep an eye on him.. Though I am starting to wonder how big this guy's going to get! He seems to grow really fast.

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