The potential negatives of an air stone/bubbler are:
-can get lodged in a fishes gills
-no GPH turns
-cause bubble algae
-cause stress to the fish (popeye)
-cause salt creep which in turn causes irregular salinity/SG
-when bubbles pop the water can get on your lights causing the life off your lights to decline rapidly,
Some periodic air bubbles are not harmful, but constant ones are.