Emerald Crab - Good or bad on my LPS?

[joe-ejs]

Hello. I recently added a couple Emerald Crabs to try and get rid of bubble algae. I noticed this yesterday. Should I be concerned? The Duncan was open as normal just prior to the crabs arrival.

Any advice is appreciated..

 

[LIreefguy]

Some people say they are bad and eat coral. I had them in my tanks for 6 years. And I never seen a coral touched Others will swear they destroy and eat coral but that hasn’t been my experience. Some will say as long as they are well feed they are ok. I never feed mine and my tanks are pretty much clear any algae

my advice is don’t put a lot in your tank. I put 5 in my 265. I put 2 in my 80 gallon frag tanks

but I tend to do that will all my clean up crew

I like to have a little of each type. Think diversity is the key to a clean healthy tank

 

[PilotOfSubmarines]

In my experience they wont EAT the coral but they will IRRITATE the coral. They eat around the polyps and cause retraction. They were annoying a lot of my stuff even in a big tank and they had to go.

Every specimen is different so your mileage may vary

 

[Sharkbait19]

It’s hard, they are hands down the best algae eater my tank has had, but also it’s biggest nuisance. Since mine died the bad algaes have started creeping back up, especially bubble. But he did eat at my corals.
Usually they are just trying to get dead flesh or algae off, but some do develop the taste for flesh.
All I can say is keep an eye on it.

 

[Sleeping Giant]

Flick it away, no need to be on coral

 

[Gtinnel]

I have had the opposite experience as others on here. I watched one in my tank pluck clove polyps and eat them one by one, although to be fair I never target fed it and I had very little algea so I'd guess it was probably hungry. I would personally be worried about it eating something directly from the head of the duncan.

 

[LIreefguy]

This question is almost like asteria stars

sone people will swear they eat zoas
But I have a ton of stars. I get get a harlequin shrimp my big wrasse will just make easy lunch of them. And if you see my post I sell zoas like crazy. They just grow grow grow
I think sometimes the coral dies because of us or just because abs we like to blame the crab or the star
I mean if you have 2 crabs in a tank and your corals are healthy and growing. Even if the crab cleans the coral once in a while because there is algae on it. How much harm should that do to a healthy coral

 

[Gtinnel]

This question is almost like asteria stars

sone people will swear they eat zoas
But I have a ton of stars. I get get a harlequin shrimp my big wrasse will just make easy lunch of them. And if you see my post I sell zoas like crazy. They just grow grow grow
I think sometimes the coral dies because of us or just because abs we like to blame the crab or the star
I mean if you have 2 crabs in a tank and your corals are healthy and growing. Even if the crab cleans the coral once in a while because there is algae on it. How much harm should that do to a healthy coral

In my case I watched the emerald crab cut the polyps in half and eat them. I didn't just make an assumption that the crabs were the reason my clove polyps suddenly died. I can say for 100% certainty that emerald crabs can eat coral. I am in the belief that if they have plenty of food that they probably won't eat coral, and if I were to have a bubble algea issue to where adding an emerald crab would be beneficial I would still be willing to add another one to my tank.

 

[BroccoliFarmer]

Ive had two different ones in the last 4 months whom i fed nice sized strips of Nori every time she was out and about. She still went after my torches and Froggies. Insatiable appetite. Persona Non Grata in my tank and i no longer keep them.

 

[LiveFreeAndReef]

Mine never ate coral, just perched on SPS all the time

 

[anthonygf]

I had a bunch of hermit crabs climb up on my branching Monti and break off branches. I refuse to have any crab in my tank. If you need to remove bubble algae or anything else just make this tool and you can scrape and suck out the algae.

It is a 1/4" stainless steel straw sealed inside a 1/2" hose, create suction and into a bucket. Replace water with new salt mix. Works great.

 

[Leadfooted]

Bottom line it's hit or miss, you'll find this to be the case if you do the research.

Personally, I've watched them eat the flesh on the flesh on my cut chalice, I've painfully watched (in disbelief) them tearing off the vessels on bounce mushrooms, they will actually store extra vessels on there legs like water weenies, funny but not funny. Some emeralds find out LPS have stomachs loaded with food, once they do, they can devour heads one at a time on corals blasto's and acans.

 

[Mhamilton0911]

+1 to emeralds being naughty. I caught mine eating my chalice, actually snipping chunks off and munching away. Also shoo'd him off of every other coral, zoas, mushrooms, rock flower anemones. Don't know if he was eating the others or just irritating them, but after he was caught red handed he was removed.

 

[JGT]

Agree, I've had the good, the bad and the ugly. Some just eat algae like they are supposed to do. But I've seen others tear into corals. I watched one small one go after a perfectly fine Duncan. Chased him away but in the morning 2 of the Duncans cups were completely cleaned out. So now I remove them when I can but they can be elusive and quick. I've gotten some out using long tweezers at night but they are quick and I don't want to destroy my aquascape. Getting a crab trap from a guy here on R2R to see if I can bag some that way. I actually find the small ones are worse than the bigger ones. Dumb youths. Their little claws can get into everything.

 

[LIreefguy]

In my case I watched the emerald crab cut the polyps in half and eat them. I didn't just make an assumption that the crabs were the reason my clove polyps suddenly died. I can say for 100% certainty that emerald crabs can eat coral. I am in the belief that if they have plenty of food that they probably won't eat coral, and if I were to have a bubble algea issue to where adding an emerald crab would be beneficial I would still be willing to add another one to my tank.

Not saying you didn’t see what you saw
But where they other factors. Did that coral have a ton of algae or detritus in it an that’s what the crab was eating. Has other corals in your tank die

all I am saying in sometimes it’s more than meets the eye. Why are my crabs good boys for 6 years and your are monsters
Yes each crab might be different but that different I don’t know I have about 10 crabs and they all are good Just saying maybe there is more than meets the eye or maybe you have a different species of crab who knows

 

[Gtinnel]

Not saying you didn’t see what you saw
But where they other factors. Did that coral have a ton of algae or detritus in it an that’s what the crab was eating. Has other corals in your tank die

all I am saying in sometimes it’s more than meets the eye. Why are my crabs good boys for 6 years and your are monsters
Yes each crab might be different but that different I don’t know I have about 10 crabs and they all are good Just saying maybe there is more than meets the eye or maybe you have a different species of crab who knows

The clove polyps were doing fine and no noticeable algea growth on them, or honestly much of anywhere in the tank at the time. If the crab cuts the polyp off and eats it what difference does it make if it was trying to eat algea that was on it instead of purposely eating the coral, since the result is the same.
I would like to point out that I had 4 emerald crabs in the tank and I only saw the one eat coral, the others kinda disappeared which makes me assume they probably starved, and only one of them was willing to eat coral to survive.
As for a different type of crab that looks like the emerald crab, I have no idea, but I will say I got it from a reputable online seller and it looked identical to the other 3 that never ate a coral as far as I know.

 

[Leadfooted]

Not saying you didn’t see what you saw
But where they other factors. Did that coral have a ton of algae or detritus in it an that’s what the crab was eating. Has other corals in your tank die

all I am saying in sometimes it’s more than meets the eye. Why are my crabs good boys for 6 years and your are monsters
Yes each crab might be different but that different I don’t know I have about 10 crabs and they all are good Just saying maybe there is more than meets the eye or maybe you have a different species of crab who knows

Well that's why I added them, I had a major GHA problem, my system has just a little age behind it lol, I assure you food source was never an issue.

I understand your happiness with them they can be a great clean up crew, but, talk to enough vendors or farm owners, most I talk to all share similar rouge experienced with emeralds. Not many of them questioned my experience so I got rid of all, too many echoed something similar.

 

[LiveFreeAndReef]

I think male vs female is a consideration to make. For people that have had trouble with emerald crabs, do you know whether they were male or female?

 

[Leadfooted]

Also for what it's worth, since I got rid of my emeralds I added about 5 times as many blue legs to keep algae at bae, I think they're actually doing better as a larger team than my emeralds did.

 

[Gtinnel]

I think male vs female is a consideration to make. For people that have had trouble with emerald crabs, do you know whether they were male or female?

I have heard that before but not until after I got rid of mine, so I have no idea.