This are Mollukken shrimps! They love high current and feed in one position.
Check this clip to see how they sit together and have a feast!
Part of my blog : Nature On The Balkoney Tour! And At Home! Aquarium, Terrarium! https://ecency.com/gems/@sandymeyer/a-place-to-calm-downafte-jegmyh5y0yo0ejj2xcr37wfngfi1wge2
Thanks for having a look and see you soon 🍀