What is this little creature in my tank?

[Reef.Blue]

I have had these little bug like creatures crawling around one of the rocks in my tank for about 2 weeks. The past 2 days I have been able to make out that the creatures have tails so I had to immediately come ask you guys on here. I have 2 fire shrimp and I began to wonder if maybe they bred. These creatures have become increasingly larger over the 2 weeks. Sorry the pictures below aren’t that great quality. Pleas let me know if the video does not work. Thanks!

 

[KrisReef]

The video worked and I did get a glimpse of a tiny shrimp like creature. Very nice!

 

[tbrown]

Looks like probably mysid shrimp. Good hitchhikers.