Emerald crabs aren't compatable with clams?

jigga w00t

A few days ago i bought an emerald crab for $5 since I've got a bit of bubble algae. Earlier today, I bought a beautiful 2" maxima for a great deal from a local wholesaler. (Don't worry my lights are fine)
A couple of hours ago, it occurred to me that the crab might not be completely safe. After tons of research, I've found a handful of clam enthusiasts have found their emerald crabs either picking at mantles, attacking or actively eating their maximas.
The emerald crab I got was pretty active at the store - avidly picking at rocks looking for food. I watched him earlier today - picking at the rocks like he did at the store. Walking around my xenias and other corals as if they were a nuisance and in his way. A short time ago I was able to locate the crab and catch him, now hes chillin like a villain.
I'm sure theres tons of reefers that have clams and crabs with no issues, but when there is a problem they post in the forums. No one ever posts "Everybody is getting along great!"
Has anyone had problems with emeralds and clams? I know you guys love maximas and I'll post a pic as soon as I can. But I just don't want some $5 crab eating my $40 maxima.


Active Member
No - Emerald crabs should not be housed with clams. I have had luck with doing it, only if I made sure that the Emerald crab was a female and not a male. You might get pinched but, on the belly of the crab is what's called a girdle. Males have an elongated one that looks like a pencil while females have a more oval shaped one usually with stripes. The females appear less aggressive, but I have still seen both male and female pick at clam mantles.


Originally Posted by jigga w00t
Thanks for the quick reply. I don't have a sump to put the crab in. What to do... what to do...

Catch it and bring it back to your LFS. I'm on a hunt for my big male in my 155G at the moment. He's behaved so far, but if I catch him, he's banished to the sump.
This is a problem with most "reef safe" crabs. They'll all behave for the most part, but sooner or later, their true colors show.

jigga w00t

Ok, thanks for the help, guys.
Here's a pic of the little guy, about 2 inches. Light blue color and those orange stripes made him stand out from the others. I got the derasa about 11 months ago and it was the same size!