Flat Circular Calcareous Critter ID

[Innominandum]

I've been noticing these flat little plates all over my tank recently. I notice them mostly on my frag plugs, base meat of zoas, and supringly on long strands of GHA. I'm not sure how much is on my rock since my rock is still tan/white-ish.

They seem very flat and I thought they were just grains of sand or coraline algae for a long time. Very up close you can kind of see a spiral in the circle so I thought it might be some kind of snail? but theyre also paper flat, so idk where the snail bodies would be.

They don't seem to fall off as easily as sand on corals. To remove them from frags, I've had to shake them very hard in the water column and brush off the remainder (usually the ones stuck to the base of zoas)

Anyone have any experience with these? or know what they are?

 

[Tahoe61]

https://www.reef2reef.com/threads/what-is-that-a-r2r-guide-to-common-new-tank-hitchhikers.443382/


Spirorbid worms?

 

[Innominandum]

https://www.reef2reef.com/threads/what-is-that-a-r2r-guide-to-common-new-tank-hitchhikers.443382/


Spirorbid worms?

Probably not right? they kinda do look like flattened spirorbid worms though. But spirorbid worms I've had in the past were thicker. These ones are about the thickness of 1-2 printer papers. They do look like spirorbid worms smashed flat though

 

[GSPClown94]

Google image search limpets and see if that is what you are seeing. There are some pretty small species of limpets that stay small. One or two of those things looked kind of like limpets but I think this might be something else.