What’s this? What’s THis? Popping up everywhere

[djohnson610]

Soo I found these little guys popping up on the back and bottom of my uv filter. Any thoughts to what it could be? I was thinking a sponge but I’m not sure.

 

[kchristensen8064]

Pineapple sponges. They are harmless filter feeders and will eventually thin out.