Anything I should worry about?

[Abijennah]

[DaJMasta]

I wouldn't, looks like tufts of hair algae to me.  You could pull them out just to reduce the spreading speed and take a look to be sure, but it's likely that if they're growing, it's not the last of them you'll see.

Depending on tank age/parameters/stocking, maybe it's no concern, and maybe changing something a bit could help prevent it from being a problem.

[Origami]

Just to be sure, if you poke at it, it doesn't retract, does it? 

[JJKK]

6 minutes ago, Origami said:

Just to be sure, if you poke at it, it doesn't retract, does it? 

My first reaction is aiptasia.  I have had them out in the open in the sandbed like OP's pictures.

[Abijennah]

no, and there are 5 peppermint shrimp in the tank that would makew short work of it, if it were apitasia

 

[DaJMasta]

I've definitely seen little aiptasia traveling around in the sandbed, but they're either brown or clear - not green - and they always look more 'organized' than that.  You can usually clearly see an oral disk and single ring of tentacles rather than a sort of tuft of tentacles.  That lower right one in the first pic is the closest to an aiptasia, but maybe 2-3x the tentacles and not in that organized fashion.

 

At least, that's how I think of them.

Even if they were something nefarious, they'd be adhering to the sand, so they'd be easy to pull out and get a closer look/see if they move or react at all.

[Origami]

On 1/13/2023 at 2:17 PM, Abijennah said:

no, and there are 5 peppermint shrimp in the tank that would makew short work of it, if it were apitasia

 

If it doesn't retract, then I tend to agree, it's some form of algae. BTW, not all peppermints are Aiptasia eaters.