I have no idea what this is

[Spaceshrimp]

I bought some live rock and i only saw this today it almost looks like a small clam because it looks to be a shell with a split

 

[Wolf89]

Mussel

 

[vetteguy53081]

Agree on mussel. Unlike a clam that filter feeds, mussels need to be fed in order to survive in captivity. These crustaceans tend to specialize on tiny planktonic foods that are rare in reef aquaria, and unless provided with sufficient food of the appropriate size, these animals will starve to death in a matter of months. If you typically feed standard fish food such as flake or frozen, it will certainly not be possible to keep any mussels for long

 

[El_Guapo13]

Definitely some sort of bivalve like a mussel or clam. Not sure about the survivability of such a hitchiker or if it has special needs other than needing something like phytoplankton or other foods meant for filter feeders. I would ask @KJ or other #reefsquad members for care requirements if you intend to keep it. Also for more detailed identification of the little guy.

 

[Malifry97]

Maybe just dose some frozen or packaged phyto. Or even live if you want

 

[Wolf89]

No benefit of adding extra nutrients to your tank to keep it alive. Seachem bottled zooplankton would work though

 

[my.PsychReef]

Type of mussel probably