Does Anyone Know What Is Growing In My Tank?

[The_Meg]

I have several of these she’ll-like things growing on my filter for quite some time now. They are hard and look like shells. I’m not sure if they’re snails or something else. The started out very small and keep growing. Pls tell me what they are, I’ve found 8 of them.

 

[lapin]

Limpet perhaps

Oh and howdy

 

[Vette67]

My first thought is that it looks like a limpet. Is the shell cone shaped?

 

[Crabs McJones]

Look like slipper limpets perhaps?

 

[The_Meg]

It’s smooth and honestly looks a little like an oyster shell, but I started with dry rock, so I’m not sure how anything could get in there ‍