Just did a water change on one of my tanks and as I went to close the lid afterwards I briefly wondered if I'd accidentally used Club Soda instead of water! You know how the bubbles send tiny droplets of water into the air from the top of the glass? It looked like that! I looked closer though and realized that where they should have disappeared back into the water they were skimming the surface and they were little brown things. I expect they're bugs of some kind (hence why I chose the "Invertebrates" section to post my question) but I don't know what they are! They're about the same size as copepods but I thought those stayed submerged.