Does anyone know what this is?

[K-pow]

I’m curious as to what the white/clear film is. It is only growing on this one rock

 

[saltyhog]

Bacterial bloom? Usually that's more wide spread. #reefsquad

 

[Crabs McJones]

Bacterial or sponge maybe

 

[GoldeneyeRet]

Looks like sponge to me

 

[45ZoaGarden]

+1 on sponge. Try blowing it away with a turkey baster. If it blows off the rock, it’s bacteria. If it doesn’t, it’s sponge

 

[K-pow]

Well it’s been on there for a long time and it doesn’t blow away. Doesn’t seem to leave that rock.

 

[reef lover]

Sponge.