Brown Fast worm-looking critters at Night

[Fierce]

Hi everybody, I noticed in my tank there are a lot of these brown insect/worm-looking critters going around at night. Are these harmful? And what are they? Thanks

 

[Dread Pirate Dave]

Hi everybody, I noticed in my tank there are a lot of these brown insect/worm-looking critters going around at night. Are these harmful? And what are they? Thanks

Looks to be amphipods. They're good guys.

 

[Baldyreef]

Dave is right they're amphipods which are a good sign of a flourishing and healthy microfauna population and a healthy reef, they can also be food depending on what fish you keep