Anyone know what these microscopic bugs are? ID

[Secky]

Hi, I’ve just finished cycling my tank and I’ve put a grain of sand under the microscope to see this? There like little bugs zooming round near/next to the grain of sand. Anyone know what it is? Is it bad or is it the bacteria that came with the live sand? Thanks :)
Here is the video of microscope:

 

[kzenoni]

Looks like pods, nice

 

[Secky]

Ah nice! Glad to hear that. That’s really amazing to see that much diversity in one piece of sand! Thanks for the reply!

 

[WheatToast]

Ah nice! Glad to hear that. That’s really amazing to see that much diversity in one piece of sand! Thanks for the reply!

They do not resemble or move like any marine "pod" I have seen (Copepods, Amphipods, Isopods). However, they seem very similar to the Ostracods I have kept in past freshwater projects. Perhaps these could be marine Ostracods (which are rare in the saltwater hobby and harmless).