Aquarium aeration and creating surface agitation
The surface level of an aquarium and it's agitation is very important and understanding why is important when keeping fish in an aquarium.
On the surface water level the water meets air, and the water becomes oxygenated through the natural gas transfer between the two. The oxygen from the air is transferred into the water which is important to all marine life, but also carbon dioxide is released from the water into the air. Fish need oxygen to breathe and as the fish breathe they produce carbon dioxide. So this transfer of gasses is important to help give the fish the oxygen they need t breathe whilst removing the carbon dioxide before levels become toxic.
When we agitate the surface water the speed at which this gas transfer occurs is sped up. And as more oxygen is introduced into the tank the more carbon dioxide is released .So in the aquarium we can use power heads of or the outlet water flow from our filters to disturb or agitate the surface water flow. Another method of agitating the surface water is to introduce an air stone that will direct air into the aquarium, the bubbles will rise resulting in surface water agitation.
You will not always need an air stone for surface agitation if you have the correct filter. Many external canister filters will create air bubbles inside the filter itself and help to circulate the tank water after the water is cleaned by the filter and returned to the aquarium.
So in summary if you have a good filter and direct the outlet flow across the surface water of the aquarium to create surface agitation, then your aquarium should be getting enough dissolved oxygen, plus the toxic carbon dioxide will be released into the air.It is for these reasons that surface agitation is so important for the health of your aquarium.