I had my filter splash the water. It was a filter for fresh water that hung on the side of the tank. The more movement you have on the surface the more O2
can get to the bottom of the tank.
"At the water’s surface, oxygen and carbon dioxide are exchanged. Carbon dioxide goes from the water to the air. This is important because the carbon dioxide concentration in the water is raised as it is produced by fish. The fish would die if the CO2
was never allowed to escape into the atmosphere.
is going from the water to the air, oxygen is going from the air to the water. This is important as it provides oxygen to the water that is needed by fish.
For this gas exchange to occur, the surface tension of the water must be broken. Agitating the surface breaks this surface tension and allows for a proper exchange of gases." ( Robert Lashlee, 2008) Properly Aerating Your Aquarium | RateMyFishTank.com