identify this mollusc

[MPLongstaff]

What is this. looks like a mussel or clam. not sure how it got in tank either. wasnt sure if its harmful to anything.


120lit 0 amm 0 nitrites 5-10nitrates kh& gh is fine ph 7.4

stock is 7 corydoras, 1 bristlenose, 7 rummynose, 3 zebra nerites, 6 cherry shrimp

 

[Essjay34 149]

It looks a bit like a barnacle but they are exclusively marine

 

[MPLongstaff]

it’s definitely alive as well. retracts when any shrimp or fish glides by

 

[kwi]

There are a few freshwater bivalves, shouldn't be harmful, you can buy them to add to tanks if you want.