What is this volcano looking thing?

[Utah tank]

 

[NanoCrazed]

Sponge...

 

[Salty Carlo]

My guess would be a sponge of some sort. I wouldn't be alarmed by it.

 

[Utah tank]

It is about one inch from my mushroom any concern there

 

[Utah tank]

My guess would be a sponge of some sort. I wouldn't be alarmed by it.

About one inch from my mushroom any reason to be concerned about that

 

[Supurderek]

Nope!

 

[Salty Carlo]

About one inch from my mushroom any reason to be concerned about that

no sponges are harmless

 

[Dan I]

That looks like a sponge. Good filter feeder, and a sign of a healthy tank.