What is growing in my tank?

[Jay1661]

Have these little white tubes that are mostly next to my heater. Started with a few, now they are everywhere! The ones that made it into the display have attached themselves to rocks.

 

[mostlysticks]

My guess is harmless pineapple sponges.

 

[ihavecrabs]

Second pineapple sponge

 

[Crabs McJones]

Sponges, looks to be pineapple, harmless filter feeders. Commonly found in the sump in higher flow areas.