Porcelain crab hosting duncan?

[KonradTO]

My porcelain crab is currently hosting a duncan frag, very funny to watch, it seems that from now and then it "cleans" the polyps or just rub its body against them. I do not have the impression that he's stealing food from him..
I had the frag for a month and its always open and happy, so it seems the crab should not pose a threat to the duncan right?
Only thing is that there are no new heads in a month, but maybe the duncan is still adapting to the tank.

 

[Cichlid23]

I would not be too concerned. I’ve seen them own hammers, torchs, blastos, etc. they never seem to hurt there host. Duncans are very slow growing corals as is. Wouldn’t be considered if it appears the same size still. Could trying feeding it mysis for faster growth.