Shells get on corals - how?

[hkgar]

Every once in a while I will notice an empty snail shell on one of my SPS corals. I can not figure out how they get up there. the flow does not seem strong enough, but there they are. I knock them of and they are always empty. Only thing I can come up with is a hermit grabs one and hauls it up there.

 

[Brieninsac]

I've seen my Diamond Goby grab an empty shell in his mouth and swim off with it. Apparently he's building something, I just don't know what.

 

[hkgar]

Decorating his burrow.

 

[Synden]

Have an urchin in the tank? They often times pick up shells to use as armor. They carry them around but often times they get knocked off as they navigate through colonies.

 

[hkgar]

Only their empty shells. I had 3 but after the GHA cleared up and the got the Coraline they became hermit crab and snail food.

Also, a Tuxedo Urchin would not be on the top of an Acropora