Fat white feather dusters??

[Zyara]

I have some small father dusters in my tank, but these ones just kind of grew out of know where. Theres a few others in my tank as well, mostly on one side. I havent added anything new in about a month.
Are they actually feather dusters? Why are they growing so quickly? My tank is only 4 months old. Parameters are stable. I do 10% water changes weekly. I like how they look but I dont want them to take over.

Thanks for any replies.

 

[Big C]

Pineapple sponges.

 

[Zyara]

Pineapple sponges.

Thank you!!

So good guy? Theres a bunch of them popping up. All over my macro algae and the side of one rock.
Do I have to keep their growth under control or is this just another part of having a new tank and will eventually pass and keep themselves in check?

 

[Big C]

You typically see them in new systems, they will die off over time. They won’t bother anything.

 

[Zyara]

You typically see them in new systems, they will die off over time. They won’t bother anything.

Thank you