Emerald crab

[jrt9430]

Has anyone experienced an emerald crab being aggressive toward fish? I have seen him eat a six line wrasse, dottyback and now my cardinal fish? I have been feeding them every other day frozen mysis shrimp. Any advice?

[jrt9430]

And a clownfish

[mr_X]

What are your parameters? Are you sure the fish aren't dying and the crab is cleaning up the mess? I've always kept them and haven't ever seen one catch a healthy fish.

[BigRedsReefs10]

You've actually seen it catch a healthy fish? Or just eating the body?

[jrt9430]

Parameters are fine.
Ammonia-0
Nitrites-0
Nitrates-20
Salinity-1.025

The fish are healthy and acting fine. I haven't seen him catch a fish swimming around. I have seen him swipe at the fish. I just got home and see him eating the cardinal. All the fish appear to be very active and healthy

[jrt9430]

Didn't think it was normal for them to catch a fish

[BigRedsReefs10]

I doubt it actually caught any fish, sounds like you have something going on in the tank causing the fish to die and the crabs just being a crab.

[mr_X]

I have watched them stick out their claws in a defense manner, but never lunge at fish. I have seen sally light foot crabs do this though. I suppose it's possible, but unlikely.

[jrt9430]

Is it possible he was hungry and got aggressive?

[mr_X]

But that hungry? I suppose it is, but you said you were feeding it.

[jrt9430]

Is every other day enough?

[mr_X]

I would think so.

[Cichlid-dude]

In my experience emerald crabs are way too slow to catch a healthy fish. Ive seen them swipe at fish before but they just srent fast enough. So im leaning towards the fish were already dead and the crab was doing what it does... Cleaning up.

[PB_Smith]

Emerald crabs are primarily algae eaters. I have read that if you start allowing them to eat a lot of meaty foods, there is a good chance they will develop a taste for your fish as well.
I feed mine the Hikari sinking algae tabs and he loves them. I break one up into thirds or quarters and give him a piece on long tweezers and he takes it right from me and chows down. When it starts to soften he packs his legs with it and will go hide, relax and enjoy a meal.
The hermits love those tabs also.
He also chows on the chaeto algae like spaghetti.
Were you making sure he had plenty of greens in his diet?

[farmerizzy]

i'm a newbie here but have enjoyed emerald crabs for years. i have seen them wrestle with snails over food but never fish. i have a flame hawkfish who ocaissionally will sit on one to catch his breath (that lack of swim bladder thing). that doesn't go to well . how is tank temp. maybe o2 depletion?

[enervate7]

As long your feeding them they won't harm your tank. They are nocturnal and will eat corals left starving . I had two emeralds. Killed my frags.


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[mr_X]

Actually, feeding them or not, it's a crap shoot either way. Though I haven't witnessed mithrax crabs eating more than invasive soft corals, all crabs are opportunistic feeders and can be predatory.