Oh I see them now. Those are harmless amphipods, I have huge populations of them in my filter socks. they are good CUC, I would keep them if you can.
Good day and God bless you!
Agree, amphipods. You want these in your tank, they are generally harmless, excellent for biodiversity and fish love to eat them. They feed on microalgae, and ifyou have a thriving macroalgae refugium, you'll often find lots of them in there with the chaeto.