spider web looking stuff on a piece of lr

[got krabs]

I've noticed this stuff the other day and can't understand what it is or where it came from. I didnt add any new creatures to my tank in a couple of weeks, which has me baffled. any help would be great

 

[@knight]

i believe they may actually be a snail species.

 

[ebeckels]

do you have anemone's If so, when they excrete it can get caught on the rocks. It's not really "spider web" looking...sorta looks like mucus! (sorry to be so disgusting...it's the only similar thing i can think of) Just curious if this could be what you are talking about.

 

[mr . salty]

Is this rock fairly new to your tank??? If so it may be curing.Spider webs on rock is also a sign of uncured rock.How does the tank smell??? What is the ammo reading???