Little disk looking critters?

[Schmitee]

Hi all, I have these disk-shaped critters covering areas of my sand and low areas of rockwork. They've been in the tank for ages and don't seem to have any negative impact, but they make the sand look bad, so I'm looking for an ID and a potential solution (predator?). I'm also thinking an increase of substrate turnover will decrease their foods source and therefore the population, but just want to know what I'm dealing with first. They're all about 3mm in diameter.

 

[MoshJosh]

Maybe? https://www.reef2reef.com/threads/a...y-appeared-overnight-on-my-live-rock.1053286/

Or maybe some sort of giant foraminaiferans?

@ISpeakForTheSeas

 

[tbrown]

I had something similar for a little bit and I believe they were a form of Sea Lettuce. Mine were bright green though, and yours appear more brownish in the picture. I ended up using Flux RX for a different algae I was dealing with and it ended up taking care of those as well. Not positive that's what you're dealing with though as yours look similar but not the same. Mine were on the rocks also, not the sand.

 

[ISpeakForTheSeas]

Maybe? https://www.reef2reef.com/threads/a...y-appeared-overnight-on-my-live-rock.1053286/

Or maybe some sort of giant foraminaiferans?

@ISpeakForTheSeas

OP, do they move at all? If not, I would assume a macroalgae of some variety.

 

[Schmitee]

OP, do they move at all? If not, I would assume a macroalgae of some variety.

No, they don't seem to move. They seem to fix themselves to the substrate and wave around in the current.

I wasn't thinking algae at all, is there a form of coralline with similar structure?

 

[ISpeakForTheSeas]

No, they don't seem to move. They seem to fix themselves to the substrate and wave around in the current.

I wasn't thinking algae at all, is there a form of coralline with similar structure?

Possibly. Coralline isn't my strong point yet. I was thinking that the disks reminded me of various kinds of brown algae or a handful of red algae species.

Are the disks connected at all (above or below the substrate)?

 

[Schmitee]

I'm not sure if they are actually attached to each other, if I pull up one, it also brings up the string of sand which is attached to and sometimes will bring up others, but that may just be because they are attached to the same grains of sand. I'll look into brown and red algae and see if any match. Thanks.