Emerald crab question

[Bartman]

I am having something of a bubble algae bloom. I understand that Emerald (Mithrax :question: ) crabs will eat it. Has anyone found this to be true? What else do they eat? Are they really "reef safe"? Will other desirables in my tank disappear?

TIA.

[venkiw]

I had the same question last month, I was cautioned that it was a hit and miss with the emarald crabs, but they are safe with reefs.

I saw mine puncturing the bubble and devour a few bubbles the very next day, but I did not see the algae population go down.

Everytime I get a chance to dip my hand in the tank, I scrap of a portion the bubble algea that is visible, and I later siphon the debri that settles to the bottom. I wear gloves as I have a couple of 8" bristle worms in my tank.

HTH

[Son Of Skyline]

They're definitely hit and miss! None of mine touch bubble algae, but they are great at eating other types of algae.

I'd recommend getting a couple of them. Even if they don't eat your bubble algae they're still great scavengers.

[Samw]

I like them. I make sure I have at least 1 and usually 2 in my tank at all times.

[Aquattro]

I just read a thread on RC where the emeralds attacked and killed most of this guy's fish! He witnessed the attack in person! :eek:

http://reefcentral.com/forums/showthread.php?s=&threadid=256421

[Samw]

I just read a thread on RC where the emeralds attacked and killed most of this guy's fish! He witnessed the attack in person! :eek:

http://reefcentral.com/forums/showthread.php?s=&threadid=256421


They do attack my fish when they are dying. The fish were doomed regardless of the crab in my case (not that I lose a lot of fish but once in a while, I lose a goby here and there when they don't eat and starve). I suppose it is possible for them to kill live healthy fish but that must be a large crab. Hard to imagine a tiny emerald taking down a decent size fish.

[Chad]

I just read a thread on RC where the emeralds attacked and killed most of this guy's fish! He witnessed the attack in person! :eek:

http://reefcentral.com/forums/showthread.php?s=&threadid=256421

I read that last night too.. Scary.. that poor fish.. and was strange how the guy did nothing.. Usualy if I turn on the lights it frightens the crap outa my crabs..

Chad

[Samw]

OK, I just read that thread. My opinion is that there is no way an emerald crab in his photo could take down and kill a healthy tang. That fish was sick and the crabs took advantage of that. Fish will usually die at night anyways. That is when CO2 is at its highest and O2 is at its lowest. When I kept freshwater fish and a fish would die, I usually found them dead in the morning. Now, was there a chance that tang could have recovered if there were no crabs? Possibly, but who knows.

[Aquattro]

Sam, I disagree. I think that if a crab got a good hold of a fish's tail, it could hang on and immobilize the fish. The fish's injuries did look like they could have happened thrashing on the rocks. I once had to remove a crab from th emouth of one of my triggers...it was major surgery outside of the tank!! I ended up needing to crush the claw with pliers to remove it!

[LostMind]

The guy said he had *6* emerald crabs in his tank and absolutely no algae...

Don't you have to feed ALL your livestock - crabs included? If there isnt enough food around, is it possible the emerald crabs can go after a meal they normally would not go for?

Just speculating, I dont have emerald crabs yet...

[Samw]

I had 6 starving emerald crabs and 1 small blue tang with no algae at one point in time.

[Bartman]

I have a Royal Gramma which sleeps lying in the same crevice in the rocks every night. She has occassionally had a chunk out of a fin. Would she be safe with an Emerald?

[Samw]

I have a Royal Gramma which sleeps lying in the same crevice in the rocks every night. She has occassionally had a chunk out of a fin. Would she be safe with an Emerald?


I can't answer that question. But I have 2 sharknose gobies now for over a year without no problems. They live inside rocks. And my blue tang is still there with no problems and I'm not regularly losing fish.

[Son Of Skyline]

As with any living animal (including humans) there are gonna be those bad apples. I wouldn't read too much into cases like these unless they start to become more common than not.

[pocilipora]

Im not convinced that these were Emerald crabs. He said he may have at least 6 of these in his tank. He didnt say he bought them at all. 6 Emerald crabs just happened to be on his live rock when he bought it... come on. What I can see is them being another type of crab just feeding on dead or dying live stock. Id say your safe buying an Emerald crab, but it is hit and miss as to weather or not they are going to eat the algae you want them to.JMO

[Diomedes]

I would my Emerald crabs in a reef, Scotty. I have seen them catch ill fish and smaller healthy benthic fish such as gobies, blennies (Never healthy tangs etc. thats crap), but as well they can also prey on corals. I have seen them attack SPS a couple of times (It is rare, but happens) One of my clients has had an emerald crab from the beginning in his 120gal reef 1.5 years ago, and I put a Hydnophora frag in there and in 30 seconds the Emerald crab was sitting there scraping away - Last Week. It destroyed the stony coral frag quickly, and then tried to move onto some other SPS frags that had been in there for months. Needless to say I removed the little rogue. And no, there was no identity problem here, though there frequently is at Pet Stores.

They will eat anything if it appeals to them. They are absolute Omnivores.
They can snack on Valonia spp. Algae (Bub.) but they rarely clean the entire tank quickly.

Destroy the Valonia with a syringe full of near boiling hot water. Remember to fill the syringe half full, then initially draw back some Valonia fluid into the syringe then pump the hot mixture back in. Tedious but effective, and you don't even have to burst the bubble.

Good Luck.
Stephen