Hello,
no – one thing it’s definitely not, and that’s Planaria.
Planaria moves around on the glass like a leech, doesn’t swim in clouds. And they are much bigger – depending on the species. In aquariums you find sizes from 4 mm up to 1 cm.
The “swimming dust” is really as small as dust particles, not even 1 mm.
By the way – today the water in my tank is as clear as before ………