Help ID please. (2 Large photos)

[Giovanni]

Tonight I was inspecting my tank after lights out. I have not done this in a while. When my red brain shrank, I found this under it on the stony part. My not like light. I have found several other in the tank on close inspection. What is it? Thanks in advance.

Here is a closeup.

 

[graveyardworm]

Most likely a foram you can find some info here .

 

[Softhammer]

Looks like a red sponge to me.