ISOPODS?????

[SimplyVibing]

Hi! I had an isopod scare a while back but it turned out to just be a snail. Now I’m worried I actually have them.
Started with copepods, when the pods vanished a second colony + bigger “things” popped up. Then I found a 3/4inch, bright purple flat critter.
Caught this video purely on accident. My LFS thinks it’s an isopod. Thoughts?

 

[KJ]

Pic too blurry for ID.

 

[Unthinkable]

Looks like an amphipod to me, here's a good explanation from algaebarn.com:
Amphipods and/or Copepods?