ID on things growing in my filter

[Byrns149]

I have several of these white tubelike organisms. They resemble whitish translucent sea squirts.

 

[bob1968]

Pineapple sponge

 

[Betta132]

Yep. Harmless, don't sting, grow in dark places and filter feed. They do basically nothing but sit there... You can poke one if you want, they feel neat.