What’s this growing in overflow?

[Super Fly]

I only see it in the overflow section. Its very long, thin and stringy. Image is same area just zoomed in twice. Anyone know what it is? Thx.

 

[ca1ore]

I have this come and go in my overflow. Always seemed like a form of sponge. Harmless.

 

[jeffchapok]

That looks like the hydroids I get in my QT tank, although much more densely populated. I suspect I only get them in my QT because there's usually nothing in it to keep them under control -- whatever eats them. The same with your overflow I presume.

If you turn off the flow, do they pulse, shrinking up and then extending again? If so, those are hydroids. If not, then I agree they are probably sponges.

Forgive the algae on the glass -- nothing in there to keep it clean.

 

[Super Fly]

That looks like the hydroids I get in my QT tank, although much more densely populated. I suspect I only get them in my QT because there's usually nothing in it to keep them under control -- whatever eats them. The same with your overflow I presume.

If you turn off the flow, do they pulse, shrinking up and then extending again? If so, those are hydroids. If not, then I agree they are probably sponges.

They dont appear to move/change size/shape. In my DT there r quite a few regular sponges growing on rocks. So I’ll assume these r sponges too then just stringy. Thx