Interesting... I looked up caddis fly larvae and it’s probably the closest looking to anything I’ve come across. The only thing is it doesn’t really look like the casing it retreats intro is made out of anything like sand or dirt and they all have the same looking casing. So it looks almost like just biological material - like a little bit transparent, greenish color. Of course they’re so small that I can’t be sure.
I took one of the “creatures” in a cup of water back to the pet store. The water still had hydrogen peroxide in it from three days ago and it’s still alive and swimming, clearly unphased by what they said would “kill of anything.” No one had any idea what they were. And sadly, they didn’t seem too concerned. One girl actually said that she likes having different bugs in her tank because it creates an ecosystem. I told her it’s one thing if you know what the bugs are and that they’re safe. Anyway, they said they would take the plants back but they don’t seem worried about quarantining the ones that they have to prevent other buyers from purchasing them and potentially killing their fish