Help, What is this?

[Kim D.K]

Hello

I want to know what is this

The two pictures are different tanks.

This creature reproduces at a rapid
The first picture was taken in the sump.

It happend fish&coral tank and It's been over a year since I set up the tank.

I think it tends to occur in old tank.

I think it's a kind of algae.

 

[Spare time]

I believe its a type of sponge. Its harmless if its what I think it is. They grow all over the dark areas in my sump

 

[Highgrade]

+1 Sponge

 

[Kim D.K]

I believe its a type of sponge. Its harmless if its what I think it is. They grow all over the dark areas in my sump

Oh I saw a pineapple sponge, but I have never seen this shape before.
It's sponge with an unusual shape.