Crab-crunching death machines

[Bill P]

I have a 30g tank, into which, I have placed 2 emerald crabs and 2 snails. There are no fish right now, because I am starving the ich, which recently ran roughshod over my tank's once-happy population (survivors are in a QT tank).

Anyway, because they seemed interesting, and because they were cheap, I recently added a Sally Lightfoot crab and a Pom-pom crab to my 30g, where I had hoped they could await the return of fish-life in a week or so.

Sadly, my Emerald Crabs immediately subtracted those additions, in an overnight orgy of predation, disembodied legs, and cannibalistic horror. They would prefer to wait by themselves, apparently.

Now, clearly I should have seen this coming. But the geniuses at the fish store told me that there wouldn't be any trouble. They had logos on their shirts, and nametags, so I believed them.

Anyway, what I want to know -- clearly, need to know -- is this: Can Emerald Crabs be trusted around other crustaceans? My Emerald Crabs seem to be quite a bit bigger than the norm. If I had smaller ones, would I have better luck with this kind of thing? Is there anything that I could do, feeding-wise that might help (During the ich die-off, I have been adding some pellets every other day or so, to try and augment the algae growth for the crabs)?

As always, thanks in advance to anyone who has a clue for me.

Best,
BP

 

[Crepe]

Emeralds seem to become more predatory as time wears on by the looks and experiences of other aquarists. Most people with emeralds toss them in the sump when they become too ornery.

 

[Hinds04]

my emerald is rather small but I do have him in with a pom pom, porcelain, hermits, and snails. I have heard that it is the lightfoots that you need to worry about lol maybe I will put my emerald in the sump on my new project when I transfer everything.

 

[guitarest]

It does not matter if they are designer crabs or your standard blue crabs; they all have the ability to eat and attack anything in the tank they put their mind too. I have blue crabs, rock crabs, fiddler, and hermit crabs in my 100gal and even the hermit will eat meat if given a chance. Granted there are varying degrees of aggressiveness in crabs due to their quickness and ability to over power their intended target but do not forget in the wild they are a aggressive predator and will act the same in the tank sometimes not even provoked.

 

[Bill P]

It's a good point that you make, G. As I said, clearly, I should have seen this coming.

Even though there are no fish in the tank right now, I have been providing a few pellets and a little bit of frozen mysis shrimp every day. That seems to have kept the mayhem in check. No new bodies, and I have even been able to add a couple of hermit crabs without incident.

My new working theory is that fat crabs are happy crabs, and that fat-and-happy crabs generally leave one another alone.

 

[missmary49]

whats a good crab to start out with then? say a smaller tank with LR, hope to eventually be coral safe.

 

[cmor1701d]

I prefer a clawless tank. If it has claws, it will use them.

 

[Bill P]

Cmor's wisdom is very great. The obvious answer to Missmary's question then, is that all crabs are good crabs, provided that you amputate the claws first. That was your point. Right, Cmor?

More seriously, I think the point here is that nature is "red in tooth and claw," even when it's in a glass box in your living room. This kind of thing is probably bound to happen every now and then, whenever you keep carnivores of any kind in the tank. If you really want to avoid it, I think the only safe solution is crab-abstinence.

Alternately, I'm having some success with keeping the crabs well-fed right now. They seem to really love Cyclopeeze (sp?). My other suggestion -- based on this hard-won experience -- would be that size of crab (and therefore of claw) may be the really important thing. Keep them closely comparable, and they seem to keep one another at bay.

 

[melosu58]

whats a good crab to start out with then? say a smaller tank with LR, hope to eventually be coral safe.

I know others have different experiences but I two sally lightfoot crabs at different times in my life and they were perfect citizens. They would eat algea and scavange waste on the substrate. That has been my experience.