no air bubbles. Is this normal or are the air bubbles not super obvious?
In theory the water dripping off the sopping wet sponges will cause an air bubble or two when it splashes.
I have had root rot, slime, algae and whatnot that tells me the air bubbles are super non-existent.
At any pet store, or walmart... Get a $10 aquarium air pump, $2 worth of Airstone, and some tubing. This will provide lots of air bubbles that you can see. Sort of like DWC deep water culture. The roots will be a LOT happier with REAL AIR.
Hydro stores have air pumps too.... but most are larger than what you will need.
If you use tap water, drop an airstone in a pitcher of water overnight to help get the chlorine out.