emerald crab

[phileep]

Hey,

Does any one have any experience with Emerald Crabs in a reef tank?. I've been reading some of the posts on this forum regarding the wave of bad publicity crabs have been getting lately. There are plenty of places for him to hide. Are they angry? Will he try and eat my tang if its sleeping on the sand?

I want to try one in my smaller 50 gallon tank that I'm using to feed up the baby tang and clone BTA's.

Any advice or observations would be amazing.

Inhabbitants:
2 x Ocerallis Clowns
1 x Regal tang (baby around 1 inch from head to tip of tail)
6 x hermit crabs

[scubadude]

Hi Phileep
Emerald crabs are generally labeled reef safe, however they are crabs and most crabs are scavengers which basically means they will settle for their food supply and comprimise if they arent provided with enough food. An emerald crab has mainly been witnessed as grazing on types of algae, so as long as you are feeding nori or some type of algae to the tank (which your tang will need too) then you probably wont have a problem. Just keep a close eye on your emerald. How big is this emerald? I doubt he would mess w/the tang while he was sleeping

[FireEater]

I've had them before. I liked them a lot and they would always be out eating on the algae off the rocks.

Mine never bothered any of the tank inhabitants. I had green ones and strawberry ones. The strawberry ones get larger than the green ones.

[Samper]

I've always kept them will no harm done. That doesn't mean that I won't ever have a problem but so far so good.

[phileep]

Cheers for your replys! xxx

The crab is quite small, about 1.5-2cm accross.

I've been feeding finely chopped Nori for a few days now. Although the tang is not very interested yet. I've also been hiding 1cm square pieces in the LR and have a strip attached to the glass with a home made 'Nori Holder Suction Cup Device'.

I'm sure the tang will work it out eventually.

Cheers.

[art_of_war]

emerald crabs are reef safe. but somehow I wish the ones I have would eat my blue damsel.

[Ninong]

Are Emerald Crabs reef-aquarium safe?

In their natural environment, I believe emerald crabs are omnivorous as juveniles but become primarily carnivorous as adults: "The emerald crab, Mithrax sculptus occurs among the branches of the coral Porites furcata and feeds on the polyps at night. It has also been observed to feed on organisms attached to seagrasses (Colin, 1978)." [ It has since been renamed Mithraculus sculptus.]

As with any of the marine animals that we keep in our tanks, their natural behavior, including feeding habits, may change to adapt to the conditions they find themselves in.

This question comes up so often that five years ago I compiled a list of anecdotal reports about problems with emerald crabs in this post. Five years ago the membership on Reef Central was only a fraction what it is today. I have read many, many more reports of reefkeepers reporting problems with emerald crabs in their systems.

I think it is correct to say that some reefkeepers have found emerald crabs to be "fairly reef safe," but it is probably a stretch to say that they are "fairly reef safe" under most conditions. In their natural habitat, they tend to be primarily herbivorous as juveniles but their diet changes to primarily protein based as they mature. They are omnivorous but they change from mostly herbivorous omnivores when young to mostly carnivorous omnivores as adults, according to various scientific papers that I have read.

Emerald crabs (Mithraculus sculptus) are sort of in the same category as the notorious Atlantic green brittle star (Ophiarachna incrassata), every time someone posts something bad about them, someone else will post that their experience was trouble-free. I suggest you read the reports summarized here and be guided accordingly. I could add at least 100 more similiar reports if I did a current search on all the boards. That was just a quick search on one board several years ago.