Emerald crabs and SPS

[takoattack]

Looking to hear from your experience on keeping emerald crabs with SPS.  I added an emerald to my 32G Biocube mixed reef tank two days ago to help with balancing my algae situation. 

I found him nestled up in my Screaming Green Birdsnest coral this morning. It was difficult to tell if he was cleaning it, or eating it.  I've read a few threads on RC this morning where some people swear that the emeralds have eaten their SPS, while others think that they are eating algae or dead bits around the coral.  There is lots of GHA around for him to eat, and he has already been cleaning some of the rocks in this area of my tank. 

 

System details:

32G LED BioCube, setup with 24hr on cycle refugium in chamber 2 with chaetomorpha and Gracilaria. I run Chemipure and purigen in the media basket. Corallife skimmer + heater in chamber 1.

Full lighting for 12 hours 9a-9p, moonighting ramps up at 7am and down to 0 at midnight.

Stocking:

Tribal Blenny, Court Jester Goby, Hi-fin red banded Goby, Splendid Dottyback, Green Clown Goby

2 small peppermint shrimp, 1 tiny candy stripe pistol shrimp, 1 Strawberry Crab, 1 Emerald Crab, 1 Strawberry Conch, ~30 various snails.

2 torches, 4 head frogspawn, purple/green hammer, GSP, large galexia, various mushrooms, Birdsnest, Pocillopora, purple whip, trumpet coral, plate corals.

Params:

Alk: 7dkh, Calc: 420ppm, Mag:1220ppm, PO4: 0.025ppm (taken right before my weekly 5G ~20% water change)

Ammonia, nitrite, nitrate undetectable with API (need to get a new low range Nitrate test kit)

Temp: 78 +/- 1.5 deg with light cycle

I've been feeding what I think is heavy: (1/2 cube total volume) once per day mixing pellets, mysis, squid, baby brine, fish eggs, phyton, and various nori flakes.

 

Thanks

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[FarmerTy]

Mine used to sleep in the birdsnest and come out to eat algae, detritus, and other goodies in the tank.

I don't think its eating your birdsnest.

That being said, it is a crab and they are opportunistic so there is always a chance.

[Gig 'em @ NDstructible]

Typically they don't prey on SPS corals, but emeralds come in different temperaments so I wouldn't be shocked if you found yourself one that has developed a taste for coral. I've had some bad ones in the past that I get to banish to the sump because they were attacking things I didn't want them to.

[jestep]

I catch mine in birdsnests as well, usually it looks like they're trying to catch passerby particles or pinch algae of nearby rocks. I do think there is a chance they could irritate them to cause damage or recession, but I haven't observed them eating undamaged corals.

[Juiceman]

Never had any trouble with my emeralds


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[takoattack]

He was hosting in the birdsnest when I got back from work yesterday, was in it all night and this morning. It actually looks like it's in better shape in the areas where he was hanging out, there was better contrast between the polyps and skeleton.




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[jestep]

That's interesting. Trapezia crabs will host acros and seriatopora and are beneficial to them. It seems like your emerald might have the same idea.

[Peter Gott]

IME, emerald crabs are the single most unpredictable animal you can put in a reef aquarium...never can tell what they're going to do next, and which ones are going to be awesome and which ones are going to be little punks. This is a new level of awesome though.


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[HarleyGuy]

In my 36 gal tank my birdsnest has gone up to coral heaven, but I think that was a case of the tank not being seasoned enough when I initially put it in, not my Emerald crab. Currently my tank is jammed with LPS and soft coral and the crab hasn't done anything negative except bump some frags off of my frag rack. ;-)

John