Crabs

[Anonymous]

I'm on a crab hunting mission after an evil little crab with sharp claws killed my velvet nudibranch.

It is very small, but large enough to kill another nudibranch and I'm sure it will be large enough to kill a sleeping fish in a few more months, so I have to get rid of it.


My question is about a very large crab I have. Its body alone is about 2 inches across. It is dark purple and black with no real markings or colors on it. It has red eyes.

It does not appear predatory and despite it's large size, I have never suspected it of doing anything to kill a fish or invert in my tank.

I think it prefers algea over meat for two reasons:

First, it has claws with flat tips. Almost cup shaped, the tips actially become flat and round at the front...like a pair of tongs.

Second, it picks algea off of rocks and coral all day and it goes nuts when I strap nori to a rock for my tang. It also goes after veggie pelets and flakes, while ignoring meat based pellets completely, even if they land right next to it. It's just like my tang in its preferences....the same type of food my tang ignores, the crab seems totally uninterested in.


So my question is...should I trap that crab while I'm at it? Are there any hitchhiker crabs that are worth leaving in the tank?

 

[Nautilus1]

Crabs can be beneficial if they are well behaved. WHich is never! I have never seen a crab that did not knock things down and kill things.

 

[fyrefysh]

I think that everyone has a different opinion on crabs. I have an emerald (Mithrax sculptus) crab that seems to be just fine and generally stays on one rock. Do you have a picture of your crab? Sounds like quite a big crab to be JUST eating algae. It may eat it's veggies during the day and preying at night, who knows? I think that crabs can be very beneficial if they are a small size.

 

[Anonymous]

I think that everyone has a different opinion on crabs. I have an emerald (Mithrax sculptus) crab that seems to be just fine and generally stays on one rock. Do you have a picture of your crab? Sounds like quite a big crab to be JUST eating algae. It may eat it's veggies during the day and preying at night, who knows? I think that crabs can be very beneficial if they are a small size.

I captured one crab last night. I used a shot glass with a tapered mouth and 10 minutes after lights out, the crab was inside. Although the mouth of the shot glass was too small for the larger crab to get inside, he did not show interest in the bait...he just walked by it and kept picking algae. The pointy clawed crab was very interested in the meaty bait though.


I will try to catch the larger crab, if only to get a photo of him. His claws have flat tips that meet eachother like tongs. I can't see how that would be useful for catching prey....that claw wouldn't even break skin unless there was a hell of a lot of power in the clamping action.


This is sort of what the crab looks like, but mine is darker with purple and more hair on the legs. The claw tips on mine are a bit flatter I think, but this photo gets accross what I mean by not pointy claw tips. The website says it is a mithrax crab.

 

[snapper1]

A crab can miss a Fish a millon times but only has to catch a Fish once,crabs seem to be primarly meat eaters I lost a clown Fish to a large arrow crab and a large crab with a large shell got a small sersi Grouper I had.Crabs are great for clean up crews but are always on the look out for easy meals.