What is breeding in my sump?

[Salties Diner]

Can anyone please identify what is breeding in my sump? I run a fine micron filter sock so the sump is generally very clean. There is no live rock in the sump so I'm not sure how they got in, perhaps when I have removed the sock for cleaning. I have tried to remove them all before, however as there would still be some in my media bag etc. they have multiplied again. What are they? How do I get rid of them?

 

[Maggie321]

Pineapple sponges

 

[saltyfilmfolks]

^^^yup^^^

 

[Salties Diner]

Thanks for the super fast response Maggie!

 

[Maggie321]

Thanks for the super fast response Maggie!

I thought we were racing

 

[Salty1962]

Sign of a healthy tank