Strange Filter Feeder??

[8pixel]

The other day, I noticed a few of these things that I thought were amphipod shells but I took a closer look today and they look like clear sacs with feathers on the end. Wasn't sure if these were good or bad but they have taken over the inside of my Phosban reactor. Nowhere else in the tank though which is weird.

Thanks, in advance!

 

[thirty6]

Looks like a pineapple sponge to me

 

[8pixel]

Thank you!