What is the swarm? ID Please

[KayBabe785]

This is the second time in 2 weeks I've seen this at night. They appear to be a new hatch of whatever they are, as they are not there nightly. The video couldn't focus on them for long but from what I can see the have a redish-orange main part of their body and a "tail" of sorts. I can't confirm if it's a singular tail or if theres two. They are very small, fast swimming, come right to the light of the camera, and definitely stay in a swarm. Thoughts?

 

[HomebroodExotics]

This is the second time in 2 weeks I've seen this at night. They appear to be a new hatch of whatever they are, as they are not there nightly. The video couldn't focus on them for long but from what I can see the have a redish-orange main part of their body and a "tail" of sorts. I can't confirm if it's a singular tail or if theres two. They are very small, fast swimming, come right to the light of the camera, and definitely stay in a swarm. Thoughts?

I’m not able to see the video but it sounds like hermit crab larvae. Took me a while to figure it out In my own tank, I thought it was shrimp larvae at first.

 

[bradleym]

They swim like mysis/mysid shrimp. Try looking those up. If so, they are not harmful, and make good fish food.

 

[monkeyCmonkeyDo]

I was thinking brine
D