What are these things?

[cicrush13]

I did a water change last night cleaned up the tank real nice and came home today to see hundreds of these little white spots on the glass that appear to be moving around any idea what these are they look like fleas or something along those lines

 

[Tahoe61]

Probably Isopods.

https://www.reef2reef.com/threads/what-is-that-a-r2r-guide-to-common-new-tank-hitchhikers.443382/

 

[Kaimana]

I did a water change last night cleaned up the tank real nice and came home today to see hundreds of these little white spots on the glass that appear to be moving around any idea what these are they look like fleas or something along those lines

A type of copepod. Tisbe are commonly seen on glass because they are benthic and like to be on surfaces. Copepods are very good to have in your system