Does anyone one what leaves these marks on rock?

[Fritz05]

I saw these marks on some of my rock, I cannot blow them off. My CuC consists of some blue leg hermits, Trochus, Astrea, Nerite, and Cerith snails. And yes, there is a vermitid snail, which I will remove! Thank you.

 

[MnFish1]

I saw these marks on some of my rock, I cannot blow them off. My CuC consists of some blue leg hermits, Trochus, Astrea, Nerite, and Cerith snails. And yes, there is a vermitid snail, which I will remove! Thank you.

Can you put an arrow/s - where you're concerned?

 

[emmysnewtank]

The same aliens that make the crop circles.

 

[dschuffert]

I am having difficulty identifying what you are looking at in the picture. Maybe you can mark them for us to see?

 

[WheatToast]

I also have this organism growing in the cryptic regions of my tank:

I am not sure if it is a sponge or not, though it really is something I would not be worried about and definitely never restart a tank over (from all that I have seen, sponges rarely become an issue, and I accept them as a part of a healthy tank ecosystem). This stuff has a pretty weak composition and lies low, so I would expect most grazing invertebrates to be capable of consuming this stuff (though I have never actually seen this happen).

 

[Fritz05]

Here, it looks like fossilized worms to me !

 

[Labridaedicted]

Rock could be an old Platygyra sp. (Or similar) skeleton. Alot of the mined rock and rock from reefs were living coral at one point. If they've always been there, I'd lean towards it being corallite remnants.

If they're new, it could be a tube warm of some kind, however, most of the marine worms that make composite tubes rather than extruding their own are sediment dwellers, (and these seem to be compsite or part of the rock) so I'd still lean towards the former.