Emerald Crab Thoughts?

TheSheff · Jul 24, 2022

Hey ive considered getting an emerald crab for a bit now and I am just curious what y'all's experience has been with them. Some people absolutely love them and some hate them bc they can eat coral. Is there something different that can be done so that they don't eat coral?

jabberwock · Jul 24, 2022

No crabs

SauceyReef · Jul 24, 2022

I have always really liked them, but do not keep them. They will most likely eventually pick at something even if well fed from my experience.

FreshCoastReef · Jul 24, 2022

Hi @kksheff, I've had an Emerald Crab for about 4 months now. I like it because he's always busy eating algae, have seen him take care of a bubble algae that made it in on a coral, and he wiped out out real fast. He did kill a photosynthetic plating sponge that I had, but I haven't seen him eating any other coral.

I think sometimes they may get a bad rap, because they will pick all around coral, for example he was really busy around my hammer when I first got it. But I never saw him actually bothering polyps, but if your weren't watching closely it may look like they're eating the coral. Time will tell.

Dkmoo · Jul 24, 2022

Mine is part of my cuc. I had a tough battle with the "long stick" kind of bubble algae and they are the only things that took care of it. That was 2 years ago and it is still alive in my tank.

Mine never attacked corals, even when it feels mischievous and takes food from corals mouths I've seen him do it with such pincer-precision that no coral tissue was damaged.

They are scavengers, which means they eat everything - but will choose the easiest food source first. My suspension for all the "emerald ate my coral" situations fall in 2 categories 1) starving crab - they need mature tanks, IMHO, with multiple types of algae and other microfauna to pick at. 2) coral tissue already unhealthy or dead/dying, and crab is just being the janitor.

chandavi · Jul 24, 2022

No crabs!! Ever!!

Uncle99 · Jul 24, 2022

Crab = Trouble.
Useless as CUC.

vetteguy53081 · Jul 24, 2022

kksheff said:
Hey ive considered getting an emerald crab for a bit now and I am just curious what y'all's experience has been with them. Some people absolutely love them and some hate them bc they can eat coral. Is there something different that can be done so that they don't eat coral?

IF you do- get a female but when it comes to these guys. . I trust a politician more than I trust emeralds LOL

Sharkbait19 · Jul 24, 2022

Emeralds are very good at their job. Most also wind up being pains. My old one killed and ate a small serpent star (watched him do it) and repeatedly pulled clove polyps off the rocks. Wonderful algae water though.
My current 2 are much better behaved.
They are good to have, but like to be annoying. Not the worst cuc member you can get.

homegrowncichlid · Jul 24, 2022

I have kept hermit and emerald crabs. Though we know hermits will die out over time, I do have some of them living over a year, possible 2 years. Emerald crabs don't last more than a few months for me, likely not getting enough food, whereas the hermit crab do better, during those times of famine. By mass, an emerald crab looks like it could be 10x or 20 x bigger than a hermit, so I would assume it needs that much more food, which explains why they will eat desirable things in your system, once the algae is gone.

Goby Bryant · Jul 24, 2022

Mine killed a yellow watchman goby.

Sharkbait19 · Jul 24, 2022

fishmanhenry said:
Mine killed a yellow watchman goby.

A healthy fish should be able to escape a crab. Most likely there was something else wrong.

Goby Bryant · Jul 24, 2022

Probably

Fredrxn · Jul 24, 2022

I had one watched it eat my torch coral ..took to lfs sameday

reefiniteasy · Jul 24, 2022

I have no clue. I can’t read minds, let alone one that belongs to a crab.

Tcook · Jul 24, 2022

I had one chomp on a scoly in the past but still keep them now. They decimate bubble algae.

TheSheff · Jul 25, 2022

vetteguy53081 said:
IF you do- get a female but when it comes to these guys. . I trust a politician more than I trust emeralds LOL

wow that says a lot lol. I love the look of emerald crabs and the way they eat/move but considering most replies in this thread are negative I guess Ill just have to watch videos about them lol..

Sharkbait19 · Jul 25, 2022

Despite the problems, I do think they are still worth getting. They are one of the most valuable members of my cuc.

mikedgrok · Aug 7, 2022

Have had a few previously... never issues... Picked one up last weekend and all she's done is go around the entire tank mowing through GHA and eating it. Was able to spot feed a nice chunk of meat last week.

I watch her climb all over coral bases, frag plugs, etc., even sometimes crawl on corals - only thing is just going for the algae around the colony. Full polyp extension on SPSs within minutes of her moving on to the next feast.

Was actually pretty cool, started eating strands of algae from the moment I dropped her in the tank - a lot of confidence I guess!

I'll tell you guys, last summer I went on a 2 week vacation, and i DISGRACEFULLY left the auto-feeder on the counter next to the tank, instead of on the top of the tank.... all fish survived (how!) and only issue I saw was some picking at the base of an SPS - maybe about a 0.25" band around it had been mowed down. Rest of coral was fine (I actually just cut it in half yesterday w/bone cutters and now have two

Anyway... all good here. Had ordered a pitho from reefcleaners - unfortunately got a female (with the huge claws) that made it her mission to eat snails and hermits and left all algae alone.

This emerald is fantastic... I have euphyllias (but not those $99999 torches), bunch of different SPSs (but not those $10000 acros) and some GSPs - no issues.