John,
Is the water you are adding flying through the air or is it being directly added. The reason I ask is because if the water travels through the air in a spray it will be oxygenated. If the water is just added in a column, it will only pick up a small percentage of the O2 it could have had it been sprayed.
18 to 24 inches of travel through air exposure equals saturation for water. It happens that fast, but it needs to be exposed to the air, so spray baby, spray.
