What are the completely "reef-safe" crabs? Are they even a thing?

[Sink_or_Swim]

Hermits are by default on the Bad list. They knock things over and hunt snails like they have a vendetta.

Sally light foot crabs I have heard rumors of them trying to snatch a fish but no first hand witnesses.

Emerald crabs are perfectly harmless.

Pom Poms only figh each other when one looses an anemone. Which is hilarious to watch.

All my emeralds have been harmless UNTIL I got the most recent one - a larger "ruby red" mithrax (aka red emerald crab basically lol). He's insane! Chopped half a leg off my serpent star and took a swipe at my tang's side, and waves his claws in the air like he just doesn't care. LOL. I'm going to have to try and catch him and back to LFS he goes.

 

[TopClamSkoo]

1. acro crab (trapezia) - Those are reef safe in my book. Had it for 2 years until I broke my tank down a while ago. Just make sure you feed it. It'll never leave your Stylo once they decide to home it. Just make sure you u have a colony and not a frag. **Please note, I did see it rip a piece of my serpents leg off but it appeared to do it in defense because the star was trying to steal the wafer away from the crab when I was feeding it.
2. Porcelain crab (anemone crab) - not reef safe! Caught his @** ripping apart my hammer head on the 2nd day! Sad part is.. he even had a decent home in my tank and was feeding it carnivore wafers! It was living in a BTA.. what gives!?!I gave it a good home and spoon fed him!
3. Porcelain crab ( filter feeder one) - Reef safe all the way!!! Great colors too! Had light colored one with blue metallic spots and had yellow filter feeders and a maroon brown one. Never ever seen them eat or attack anything! Just hides all day and you'll never see them unless you look behind ur rocks to spy on them. Had them for couple years! No issues! Just feed em cyclops and they'll be fine.
4. Emerald crabs - never seen them do anything bad.. but go scared from other stories so I took them all out and never kept them again.

*just my experience with these..

 

[Sink_or_Swim]

1. acro crab (trapezia) - Those are reef safe in my book. Had it for 2 years until I broke my tank down a while ago. Just make sure you feed it. It'll never leave your Stylo once they decide to home it. Just make sure you u have a colony and not a frag. **Please note, I did see it rip a piece of my serpents leg off but it appeared to do it in defense because the star was trying to steal the wafer away from the crab when I was feeding it.
2. Porcelain crab (anemone crab) - not reef safe! Caught his @** ripping apart my hammer head on the 2nd day! Sad part is.. he even had a decent home in my tank and was feeding it carnivore wafers! It was living in a BTA.. what gives!?!I gave it a good home and spoon fed him!
3. Porcelain crab ( filter feeder one) - Reef safe all the way!!! Great colors too! Had light colored one with blue metallic spots and had yellow filter feeders and a maroon brown one. Never ever seen them eat or attack anything! Just hides all day and you'll never see them unless you look behind ur rocks to spy on them. Had them for couple years! No issues! Just feed em cyclops and they'll be fine.
4. Emerald crabs - never seen them do anything bad.. but go scared from other stories so I took them all out and never kept them again.

*just my experience with these..

I may get one of the filter feeding porcelain crabs someday... but will NEVER keep a red "emerald crab" again. Currently have a big, aggressive ruby mithrax crab who chopped off one of my serpent star's legs and took a swipe at my tang. He swipes at anything that swims too close to him. Ugh.

 

[Wasabiroot]

Emerald crabs are great. They just need to either have enough algae to keep them fed, or get some nori, and they stay reef safe.

I agree. My big ruby emerald holds his claws up excitedly because I give him a small square of nori every few days. Otherwise, he lazily picks at my leptoseris...

 

[JasonVH]

When feeding the corals, I also target feed the pom pom crab. I'm guessing when it comes out during those times, it's super hungry. If it doesn't find something floating around, it sometimes targets a coral and reaches into their mouths with the legs. Target feeding it at the same time put a stop to that.

 

[kevgib67]

Always had emerald crabs, work horses and entertaining to watch, never had a problem. I have a mix of dwarf red and blue legged hermits, model citizens. I just bought my first porcelain crab, fun to watch filter feed.

 

[Alexopora]

In my personal opinion, the hermits I’ll allow into my tank are only two types. Clibanarius Rutilus (Red hermit: honestly one of the best behaved and best cuc ever) and these unknown but small semi-filter feeding hermits. Clibanarius Rutilus are voracious algae eaters and basically the rock work is their home turf. They’ll tackle hair algae as well. As for the smaller hermits, they love to bury most of their body into the sand and filter feed but will engage in sand sifting as well. Cant say if they are entirely snail safe as the the only three snails I have in my tank are those small limpets, trochus snails and nassarius, which are all either two fast or constantly on the glass for the hermits to attack. Additionally trochus snail shells and limpets obviously do not appeal to the hermits.

 

[Holy handgrenade]

I love my blue leg hermits when they are small. When they get big, they seem to have a taste for my snails regardless of all the old empty shells and algae to eat.
I came back from a trip to the florida keys a few days ago and was able to get as many blue legs i want! (The legal limits)
Just got 2 emerald crabs today, couldnt find em where i was snorkeling, but im crossing my fingers and hoping they behave.
Anyone have Halloween hermit crabs? Where do you get shells for them?

 

[Holy handgrenade]

Also want to add that red mithrax (red emeralds) are straight-up gangster. Had no hesitancy to cause problems in my tank

 

[WheatToast]

Where do you get shells for them?

https://www.reefcleaners.org/aquarium-store/tank-cleaners/6-empty-cone-shells-detail

 

[JoJosReef]

I don't know what a micro decorator crab is, but I bought a decorator crab with sponges from ReefCleaners and that amazingly interesting crab picked at every coral it went by. Landed next to an acan when it went into my tank and immediately went at it, then the blasto, even the RFA, and last straw was the scoly. Watched him do it and shoo'd it away each time. Donated to a local reefer.

All emeralds I've received from ReefCleaners have behaved with corals. The one emerald I got from AquaSD took a chunk ot of my crocea (RIP), chewed palys, and saw it put the end of a torch polyp in its mouth when the flow was off. It had plenty of algae to eat and actually did a notably amazing job on the bubble algae but truly had a casual attitude about tasting corals as it went by. Donated to LFS.

My one "naughty" blue leg hermit was highly suspected to be killing my nerites and other snails while I was blaming the Eunice worm. Donated to a local as an extra freebie and snail survival went up.

Pom poms (2, one in each nano) have been on good behavior, but one has no pom poms.

Porcelain crab (green) and spotted nem crab don't eat corals or nems, but they do walk over them. Doesn't seem to bother the SPS. In fact, the nem crab often hangs out on the shady side of my potato ship pavona and it doesn't seem to mind. They do get territorial, though. Green porcelain especially bullies the poor pom pomless pom pom crab.

Gorilla crab. Had one live in my IM 10g AIO filtration chamber (likely snuck in on a piece of rubble kept for biofilter). Lived there for 10 months till I finally caught it and gave it to a local reefer with a real sump.

Not reef safe. Sump safe.

 

[JoJosReef]

Side note: I have heard that female emerald crabs are less aggressive than males which may be a factor in the mixed reception.

John from ReefCleaners thinks this is a myth. His opinion from May, I think, when I asked him.

 

[WheatToast]

I don't know what a micro decorator crab is, but I bought a decorator crab with sponges from ReefCleaners and that amazingly interesting crab picked at every coral it went by. Landed next to an acan when it went into my tank and immediately went at it, then the blasto, even the RFA, and last straw was the scoly. Watched him do it and shoo'd it away each time. Donated to a local reefer.

Agreed! Sounds like a super interesting creature that I would want to try out at some point. Perhaps the micro decorator is safer due to its smaller size and inability to carry large objects, but I’ve never owned these crabs to know for sure.

Not reef safe. Sump safe.

Are you sure they’re sump safe? There are reports of massive gorilla crabs cutting through PVC pipes .

 

[JoJosReef]

Agreed! Sounds like a super interesting creature that I would want to try out at some point. Perhaps the micro decorator is safer due to its smaller size and inability to carry large objects, but I’ve never owned these crabs to know for sure.


Are you sure they’re sump safe? There are reports of massive gorilla crabs cutting through PVC pipes .

One I got was a lot bigger than I was expecting. See here in an Evo 13.5g:

 

[StatelineReefer]

I don't believe any crab is truly reef safe.

"If it's got claws it's got flaws"

 

[Kiui1849]

Na I used to work at a LFS, so when I say things like " Ive never heard anyone say" I mean in my years of working with many people daily. Crabs decide what shells are suitable for an upgrade. The fact you provided a few selections doesnt mean he will choose them over the snails shell. Sometimes they just want the meat. And in response to "well if you fed them enough"...you arnt supposed to feed a clean up crew. If you do they wont clean up.

After selling every crab mentioned here hundreds of times over you start to see trends.

Things like, 95% of the time someone blames a crab(or anything) for eating a fish. The fish was already dead. Exceptions exist, like arrow crabs. Those jerks will spear a fish like its sport. But hermit crabs not being worth it is on that list of trends I stand by.

Side note: dont buy staghorn hermits. The coral always dies and the crab usually ends up in a snail shell because its way easier to carry.

What's your opinion on emerald crabs and sally leg crabs? I have a smaller tank with a male clown and some corals and wanted a good crab to clean up but don't want to risk my clown's safety. (Or the corals) I heard Sallys are very opportunistic and will snatch at smaller fish and I've heard mixed opinions about the Emerald crab. I just don't want him to get eaten because the tank's too small. (15 gallon, 1 clown, a duncan, and green star poylp btw.)

 

[kevgib67]

In 17 years of reefing I have had an emerald crab for most of it and have never had a problem. On this forum they recommend getting a female one but I’ve never sexed them.

 

[Poseidon Johnson]

Just found this hitchiker crab in my live rock, I think it's a helmet crab, same size and shape as an emerald but it's red and hairy.

 

[Poseidon Johnson]

 

[Poseidon Johnson]

Sorry for the poor quality photo it's night time and I used the flash on my potato.