emerald crab eating sps???

I recently got one as a hitch hiker on a rock. He was good for about a week or two, but he began eating the base of my sps. I snagged him out one night and threw him in my sump only to wake up the next day to my skimmer cup overflow alarm ringing... He climbed into the are intake venturi of my skimmer and caused it to overflow. I gave him away.
 
Or lps-they will go rogue had a master scoly that was ripped apart-expensive lesson- nutrient control much better option for algae control
 
I am wondering the same thing... This literaly happened over night on my BOP birdsnest frag.

The only change was the recent addition of a emarald crab. Looks like it was stripped with a wire stripper...

Over the past week it seems to be growing back however. Just was really shocked.
 

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I have always had good luck with them, but they do get fed. They would rather eat algae and scavenge IMO, but they aren't going to starve. If you have one in your tank, just make sure and feed it - algae, pellets, mysis are all good foods.
 
I've always had good luck with them as well. But there is generally something for them to munch on in the tank.
 
Well what do you expect when there's nothing left for them to eat? Blue tangs eat zoas when they are starved. I never had problems with them as long as it had some algae to eat, they eventually died on me when I ran out of algae though.
 
I keep and have kept dozens of Emerald Crabs for more than a decade. I have never seen that behavior in my tanks. Are the claws of that crab flat and rounded on the end? Is it possibly not a Mithrax?
 
I can confirm, 100%, that some mithrax (definitely) will scrape SPS to the point of serious damage. The bigger ones seem 5o be worse.
 
Reading some of the above post I got the impression Emerald crabs and Mithrax crabs were two different species...

Are they? After researching Ive came across this:

Emerald crab - (Mithraculus sculptus)
Emerald crab - (Mithrax sculptus)

Both come up with the same description and it seems they all reference together full circle. Either way, the attached pic is what I have.

Just to be clear, I am not 100% certain it was the crab and it is fed enough that it should not be trimming my trees.

I just found it odd that the night before I saw the BOP BN and it was fine and in the morning it looked like the pics. No crazy temp, alk, ph, sal, etc.. swings, so it raised the question.
 

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Those look like the ones that I have had success with. Mine clean up the algae and then forage for meaty scraps. I have no doubt that some can turn bad, but I have seen nearly every kind of tang turn into a coral eater - especially when underfed.

You see a lot of them in new tanks with dry rock, frags on plugs with no life anywhere and people wonder why they won't just die waiting for algae.
 
^ I agree. The tank the crab is in is only 4 months old and was started with dry rock and sand. I seeded it with live rock rubble from my other established tank in hopes to speed things up a bit, although it is SLOW going.

I do have algae growth mainly towards the bottom and am currently battling a little hair algae at the moment, but it does snatch up un-eaten pellet food daily.

I will say for only being a single crab he does a great job keeping things pretty tidy along with my blue leg; so that is a plus. I will just keep an eye on him.
 
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