Coral Beauty Angel acts weird around crab

[polysacman]

Has anyone ever witnessed their coral beauty acting weird around their other tank in habitants. I introduced 2 new emerald crabs into my 70gal about a month ago, and since that time I've been catching my coral beauty swimming up to 1 in particular, kinda of hovering around the crab, and shaking its fins back and forth real fast... almost looks like it would if it was being electrocuted. He'll do it for about 10 seconds then swim off... he's shy about it and wont do it if I get too close to the tank. My guesses are some sort of weird mating ritual, a show of dominance, some sort of request for cleaning like at a cleaning station...

Anyways, completely baffled by it and was hoping someone else might have caught theirs doing the same thing or perhaps know what is going on.

[suta4242]

Not tail fanning is it?

[polysacman]

Not entirely sure what tail fanning is, but he's fluttering really fast his tail, his dorsal, his two little arm fins (don't know what they're called) :)

[MatthewLaw]

tail fanning for aggression/dominance is usually when the aggressive fish gets near the other fish at a 45 degree angel. the aggressive fish JUST moved his rear fin and seems to shake his body too.

i have seen this with clown fish asserting hierachy.

[ginger7286]

Sounds to me like he is sizing up a meal. Haha. Seroiusly maybe the emerald crab invaded what the beauty thinks is his territory.

[TheH]

Does it look like he is trying to get the emerald crab to clean him? Like a fish would act around a cleaner shrimp?

[polysacman]

I thought it might be a show of dominance as Ginger suggested, but he doesn't do it to both crabs... and they roam around the tank, and he doesn't do it to any of the other fish. Though the other fish don't swim through all of the crevices in the rock, and the crabs do.

That makes me think it is as TheH suggested, but it just seems far fetched that an emerald crab would be cleaning fish... more like eating them :)

The crab doesn't seem to mind, he usually holds one of his claws up but doens't act threatening, and they never come to blows.