What are these white strands?

[BxstardXI]

Ive absolutely never seen this before,
I dont know if its an algea or something else but its growing under my rocks, it looks like cobwebs.

should I be worried? What can I do against it if its not good??
If it is fine I'll leave it as it is

Thanks

 

[DDenny]

I have some in my tank as well and I believe they are sponges. Completely harmless most of mine disappeared. Only place I see them in is the sump side of my AIO tank.

 

[vetteguy53081]

Ive absolutely never seen this before,
I dont know if its an algea or something else but its growing under my rocks, it looks like cobwebs.

should I be worried? What can I do against it if its not good??
If it is fine I'll leave it as it is

Thanks

Looks to be tube worms and to verify, when you feed, you will see little mini fans emerge which they use for feeding

 

[BxstardXI]

Looks to be tube worms and to verify, when you feed, you will see little mini fans emerge which they use for feeding

Ive got a few incredibly small tubeworms in my tank, the mini fans are red-orange ish. These do not seem to have anything coming out of it

 

[BxstardXI]

I have some in my tank as well and I believe they are sponges. Completely harmless most of mine disappeared. Only place I see them in is the sump side of my AIO tank.

Ohh sponges! Perfect, means more filtering haha. Thank you so much