Popping up in my skimmer

[Benga]

I found larger versions of these in-between some rocks but took them out. I'm seeing them pop up in my skimmer now. If I had to guess it's a filter feeder of some sort

Should I be worried, are they problematic? Are they an indication to anything in particular?

 

[Crabs McJones]

Sump sponges. Common. They tend to show up in higher flow areas. Signs of a healthy system