Sand columns?

[pynakerm]

Can someone assist with what is going on here? It looks like the sand is standing in columns! Thank you!

 

[Timfish]

Just some worms building themselves some homes.

 

[EeyoreIsMySpiritAnimal]

Can someone assist with what is going on here? It looks like the sand is standing in columns! Thank you!

These worms are in the family Chaetopteridae and genus Phyllochaetopterus.
See this article for more info: https://reefkeeping.com/issues/2003-05/rs/index.htm
Section-"worms with two tentacles"

 

[Idech]

These worms are in the family Chaetopteridae and genus Phyllochaetopterus.
See this article for more info: https://reefkeeping.com/issues/2003-05/rs/index.htm
Section-"worms with two tentacles"

Are they desirable ?

 

[EeyoreIsMySpiritAnimal]

Are they desirable ?

Yes and no. Read the section I mentioned. They are good detritivors but they reproduce rapidly and their tubes can make mats in the sand.
Once they're in the tank, you're unlikely to get rid of them. I have a bunch and just stir up sections of sand periodically to keep the sand loose.