Critter ID - Help please

[SereneAquatic]

Can anyone tell me what this is? I've never seen them in the tank before, and this morning they seem to be EVERYWHERE in the corner where I moved the acrylic box with the molted (?) crab.

They seem to have an identifiable spine, a couple long antennae, a set of 'feet' near the back end and walk kind of hunched or curled around themselves.

Are they harmful?

Pics attached.

 

[JWClark]

Amphipods. Harmless. Fish love them. The "spine" is actually the gut--like in a shrimp.

 

[mcgyvr]

Bookmark this for future use.. Has most of the common stuff as well as a simple "good/bad" rating system..
https://www.lionfishlair.com/hitchhikers-guide/

 

[Steve175]

Yep: you have had pods but didn’t know it. They are a good sign for the tank and an excellent source of food for the fish. In addition to nitrogen export, these guys are the main reason many keep a refugium.