What are these sand/gravel tubes?

[TimJ]

Anyone know what these are? They are tubes made out of gravel running from my LR into the sand bed. they are not hard\calcerous.…they’ll break when I touch them with a turkey baster. Noticed a lot more of the, since adding CUC snails.

thought probably spionid or feather duster worms but never seen anything come out of the tubes.

 

[HankstankXXXL750]

Spionod would be my first thought I have some similar and haven’t paid attention to wether anything comes out. Otherwise I don’t know.

 

[TimJ]

Thank you. Doesn’t seem to bother anything. Just curious if I have an infestation of Something bad waiting to happen