do you have an air pump with airstones or anything like that? i have bubbles in my tank but they are coming from the pump i would still do a water change tho good luck
I get air bubbles on the top of my tank because my air stone is near the water outlet for my filter. Usually goes away the day after a water change though.
i would say either not enough surface agitation oorrrr maybe high amount of dissolved solids in your water.. i duno if that's a problem in fresh water tho.