[featherduster1]

Just a shout out to see if anyone knows a way to get rid of bubble alge. I have tried snails and a sally lightfoot crab. As for the other fish in my tank I have a false percula, 2 black and white stripped damsels, yellow damsel, domino damsel, sail fin tang, mimic tang, copper banded butterfly, sand sifting star fish, three feather dusters, coral beauty angel, and a cleaner shrimp. I have a 75 gallon fish tank and the bubble alge is gradually taking over my live rock. I have heard that an emerald crab will eat the bubble alge but don't know if it would get along with my sally lightfoot crab. If anyone has any suggestions please let me know. If you need any other details on the tank just ask.

[Ninong]

Hi featherduster1,




Some people have reported that their emerald crabs (Mithraculus sculptus, formerly called Mithrax sculptus) ate their bubble algae (Ventricaria ventricosa, formerly called Valonia ventricosa) but I don't consider those crabs to be reef-aquarium safe.

In my own experience, the Foxface Rabbitfish (Siganus vulpinus) eats bubble algae. I have never really had a problem with it at all but occasionally when I would remove one of the upper rocks to rearrange things, I would sometimes see a few bubble algae growing in spots that received some light but that were not accessible to my rabbitfish. My tank was 120 gallons and I considered it to be a bit on the small side for my rabbitfish once it was fully grown. Mine went from about 3" to about 7" in approximately two years.

[Samper]

I'm glad you keep up with alpha taxonomy. It keeps me on my toes. I've seen the Mithraculus sculptus eating Ventricaria ventricosa time and time again in many different reef aquariums. Heck yesterday I saw one of mine eating some but only the skin. They never eat anything larger than around 1 mm. The problem is they don't just eat the entire bubble. They pop it first and then eat the outside this may spread it faster. I haven't heard personally from anyone who has ever had a problem though with the green emerald crabs. Some of them including my own have been a good size slightly larger than 2".

[Ninong]

Originally Posted by Samper

They never eat anything larger than around 1 mm.

Did you really mean 1 mm or 1 cm???

The problem is they don't just eat the entire bubble. They pop it first and then eat the outside this may spread it faster.

Which wouldn't be a problem at all if they only eat the ones that are around 1 mm because they wouldn't be mature enough to contain spores. In fact, I wouldn't even be able to see the 1 mm ones without a magnifying glass, considering how bad my eyesight is.

I'm sure you probably meant 1 cm, right?

In any case, popping mature thalli can result in spreading the problem throughout the tank. It's possible to remove them by hand without popoing them if you're careful to hold them firmly, but not too firmly, and gently twist and you gently lift to get the holdfasts to release.

I haven't heard personally from anyone who has ever had a problem though with the green emerald crabs. Some of them including my own have been a good size slightly larger than 2".

In their natural environment, I believe emerald crabs are omnivorous as juveniles but become primarily carnivorous as adults: "The emerald crab, Mithrax sculptus [ it has since been renamed Mithraculus 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)."

As with any 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.

[Samper]

Yes I did mean 1 cm. Sorry about that. When I get around to it I remove a few by hand but they have to be a good size to get a grasp on. Like you mentioned it can be done but I usually pop a few at the attachment point. There are a few people here who inject a few at a time with muriatic acid via syringe and tiny needle but I haven't ever had them bad enough to even consider that option. That's something my old partner advises people to do. I'd rather rely on good water quality personally.

I kid you not when people come over they usually ask what they are and everyone thinks they're beautiful! They aren't bad looking but it drives me crazy that they like them with all the other eye candy.

As for my own observations of the emerald green crabs, I know that one day I could eat those words. I've had them for a few years now with no harm done.

[zhenya]

Originally Posted by Samper

As for my own observations of the emerald green crabs, I know that one day I could eat those words. I've had them for a few years now with no harm done.

You've just been lucky, Chuck.
I personally seen one of these buggers sitting on top of the acropora branch tearing polyps off in one of the tanks in LFS. I told one of the guys working there about it but he said it doesn't do a whole lot of harm and that it eats thier bubble algae in the tank. Now, I should have asked why was it eating polyps instead because there was plenty of bubbles to go around, but I didn;t.