Mithrax crab?

[Latte]

Hey all, new to the hobby and setting up my first tank with live rock. I noticed a crab in the rock and took a picture of him, before (stupidly) placing him back into the cycling display. I did some research after and have spent the last week trying to catch him with shrimp in an inverted bottle and glass traps with no luck. I've got some videos of him - it looks like he's not a gorilla like I first thought, and his behaviour seems to be crawling around the live rock eating algae as you can see in the red light videos.

I'm sorry I can't get a better picture, I've been trying to catch him and it's driving me insane.just trying to work out what he could be, and if my late nights hunting this tiny crab are actually a good use of energy or if I'd be better off letting him do his thing in my rocks. He's quite small, maybe a couple centimetres across, and I'm hoping to add a few other inverts and small fish to the tank without him chomping away.

Would appreciate any help or advice!

 

[Latte]

Oh - in case you can't spot him

 

[Bombschell]

A little emerald crab from what i can see. I sure if you could get that video under regular light someone would be able to tell right away.

 

[Latte]

A little emerald crab from what i can see. I sure if you could get that video under regular light someone would be able to tell right away.

Thanks for the help, is there any key difference between emeralds and mithrax? On the video, I would if I could... The only way I can get at all close to him without him scuttling off into the rock is at night with that red light on. Maybe he'll become calmer after sitting in the tank for a while and I can do that.

 

[Latte]

A little emerald crab from what i can see. I sure if you could get that video under regular light someone would be able to tell right away.

If it helps - he has black tips on his claws (which is weird, I think that's a sign of a gorilla crab?) but he isn't hairy at all, and doesn't have those big meaty claws just quite flat narrow claws he uses to eat off the live rock from what I can tell.

 

[Bombschell]

Yeah that is why I figure if he could get a good pic or video under normal light someone would know immediately

 

[kittenbritches]

Emeralds are mithrax crabs. They come in emerald or ruby. I think it looks like an emerald -- I've never had trouble with mine and intentionally put them in my tanks. Some people don't trust them, but they've always been helpers in my tanks.

 

[Bombschell]

Emeralds are mithrax crabs. They come in emerald or ruby. I think it looks like an emerald -- I've never had trouble with mine and intentionally put them in my tanks. Some people don't trust them, but they've always been helpers in my tanks.

I've been thinking about getting one, bit have seen reports of them nipping zoanthids

 

[Soryu]

Looks like a free mithrax, as long as he doesn't nip at corals he's your friend.

 

[kittenbritches]

I've been thinking about getting one, bit have seen reports of them nipping zoanthids

It's never been an issue for me. YMMV ;)

 

[vetteguy53081]

I've been thinking about getting one, bit have seen reports of them nipping zoanthids

Agree on emerald and a word of warning- These guys are hard to trust. They are either good workers or coral destroyers. A game of hit and miss.
I personally trust a politician more than I trust a Mithrax

 

[Latte]

Emeralds are mithrax crabs. They come in emerald or ruby. I think it looks like an emerald -- I've never had trouble with mine and intentionally put them in my tanks. Some people don't trust them, but they've always been helpers in my tanks.

This one is more of a brown with a hint of grren, I suppose (especially as it is quite juvenile) that could be kind of emerald-ish I guess?

 

[vetteguy53081]

This one is more of a brown with a hint of grren, I suppose (especially as it is quite juvenile) that could be kind of emerald-ish I guess?

Typical colors for mithrax

 

[Latte]

I've been thinking about getting one, bit have seen reports of them nipping zoanthids

Looks like a free mithrax, as long as he doesn't nip at corals he's your friend.

It's never been an issue for me. YMMV ;)

Agree on emerald and a word of warning- These guys are hard to trust. They are either good workers or coral destroyers. A game of hit and miss.
I personally trust a politician more than I trust a Mithrax

Ok so seems like it's a crab to crab thing - I wonder if I can grow to trust him after a while of good behaviour or if he will still go rogue someday and just start chomping on coral? I do have some hitchhiker paly/zoas in the tank that came with the live rock

I suppose that's as good a test as any. Though they've been mostly-completely closed up for some days now, it is mid cycle though and I'm still reading very high ammonia so I'm sure it's more likely that than our clawed friend.

Regardless, I plan to add some sort of refugium to the tank over the holidays, hopefully I can trap him before then and rehome him somewhere he can eat algae until he pukes ;).

 

[Latte]

Typical colors for mithrax

Ahh ok, appreciate it. Sounds like that's what I've got on my hands, much happier than when I first thought it was a gorilla crab! (I'm very new)

 

[vetteguy53081]

Ahh ok, appreciate it. Sounds like that's what I've got on my hands, much happier than when I first thought it was a gorilla crab! (I'm very new)

The bad crabs will usually be hairy and/or have black tips on their claws

 

[blaxsun]

I have a 2.5" (not a typo) male emerald crab. He's a freakin monster - when I got him 3 months ago he was only 3/4"! So he's been apparently eating very, very well. Ignores all fish, other inverts and all my corals (including zoas). Mine has hairy rear legs and black tips on his claws, too - so I don't think that's indicative of anything.

 

[jaganshi066]

Agree on emerald and a word of warning- These guys are hard to trust. They are either good workers or coral destroyers. A game of hit and miss.
I personally trust a politician more than I trust a Mithrax

Mine ate my alveopora and gold hammer

 

[Soryu]

Mine ate my alveopora and gold hammer

Mine cower under the anemone after seeing the anemones eat half a dozen peppermint shrimp.

 

[Latte]

I wonder if I could somehow target feed him to keep him happy?