Any clue what this is?

[bun]

My tank is getting more mature and I am starting to find new things in it.

Does anyone know what this is? It looks like a gasket or a thin flat cheerio.

 

[bun]

My tank is getting more mature and I am starting to find new things in it.

Does anyone know what this is? It looks like a gasket or a thin flat cheerio.

 

[bun]

 

[Coral Your World]

Sponge, harmless, but will spread and can sometimes smother things. Can definitely just let it be. If it’s on a rock that can be pulled out easily, you can pull it out, give it a little brush to remove and rinse off with some clean saltwater and back into your tank