Mithrax hanging out in Acro. ?

[Tang Salad]

Hey-

Three days ago I put four small Mithrax crabs into my 110 to try and help with a bubble algae (Valonia) problem. I found today the largest of the four is hiding inside an Acropora colony. This largest one is about an inch across.

It doesn't look like it's eating the SPS. It's just hiding out inside. I know that Mithrax are primarily algae eaters, especially when young, but as they mature they can pick at corals. Further, by all accounts I've seen, the four I added are still well within the 'safe range'.

Has anyone else found Mithrax acting like Acro crabs, hiding inside a colony?

Apart from keeping a watch on it, should I be worried?

Any other opinions on Mithrax in general?

Thanks!

 

[Tang Salad]

Disclaimer: I hereby affirm and attest to my understanding that all crabs should be considered opportunistic omnivores and that past performance of any one species is not necessarily indicative of future results. This is the first time I have intentionally added any crab to my tank.

 

[Frick-n-Frags]

Maybe that's the safest hiding spot it likes.

Mithrax crabs are weird. they go anywhere. When I used to have a big Turbinaria, many mornings I would see the tracks across it from the crabs and in an hour or two they were gone. Mine have crawled all the way up blade gorgs = totally retarded looking like a bear in a little tree. They have even hitched on snails to get at something higher up on the glass, and of course the snail starts turning its shell to lose the crab = totally retarded looking like some mechanical bullride.

I have also nervously watched them work an SPS. They crawl all over it and occasionally find something that needs to go, but all-in-all the corals benefit hugely by always having clean bases and whatever small ding they make in the coral flesh alwways closes up quickly, even Acros.

If you want to see something go after Acros, check out those little black crabs that hitch in on Acro heads. I had an Acro frag that had like 3 nice branches growing with nice blue tips. I started noticing the tips seemed raggedy and more whitish. After like 3 days I could tell they were getting shorter, so I started doing flashlight checks. There it was, cutting through the Acro tips like it was munching off a kit-kat bar. The thing would then evidently hide back in the big head during the day because I never saw it before that night. I immediately crushed it with great prejudice.

my mithrax also go after superglued stuff with a vengeance. I'm guessing their programming that says "if it isn't healthy live coral, destroy it" kicks in when they hit this stuff next to the coral. As a result supergluing anything to glass is pointless. They will tear it off and toss it in the back where I can't even see it. I think the stuff glued to rocks is too tough for them.

anyway, after having many many of them over the years, nothing they do anymore shocks or surprises me. Mostly they throw things off the cliffs at night. I wouldn't worry unless you are actually seeing some obvious damage that isn't going away.

 

[McCrary]

My mithrax crabs are all pretty large (if they get any bigger I am seriously considering eating them), but even when they were small they didn't hide in the acros. I did have one rest on a scroll coral so often that the thing started to get damaged. If I could redo the whole thing I probably wouldn't have added them. They like to break off any frags that I glue to the rock and throw them to the sand. In a 30" tank that can be a pain in the butt. But in a SPS tank they seem to just keep to themselves and not bother anything.

 

[Frick-n-Frags]

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[Tang Salad]

Thaks for the great answers guys. I will be keeping a close eye on them.