Guppies, sword tails neon's swimming along the water surface. Pump flowing making good drop into water, lots of air bubble. All levels okay. They do not do this all of the time.
if all the water parameters are good and you think the water is well oxygenated, then i would guess they are skimming the top in search for food. (not that you need to feed them, it is normal for a fish to be looking for food.) my guppies love trolling the top of the tank to see if there's any tidbits lurking.
Fish usually swim along the top of the tank when they are low on oxygen, this varies from tank size and how much water is actually filling the tank up. It might seem like alot of bubbles, but then again, we aren't fish, so even if we see the bubbles, the fish could be slowly suffocating. Psychologically, maybe the fish feel safer when swimming to more shallow water levels?
What I find with my guppies is that if you have larger fish in the tank, the smaller fish seem to swim right in the corner, either straight at the bottom or along the top. This could also only be the fact that they are scared of the surrounding or something which happened.
Try watching them from a distance where they cant see you (Remember! fish have really good eyes!) and see if they still swim along the top.
Fish only have a few things on their mind, getting eaten, eating, mating, etc.