Question about aeration and surface agitation

[firthy13]

my 4x2x2 is in my bedroom at the moment. i'm currently using two small air stones in each of the rear corners of the tank. i have a very quiet pump but the noise from the bubbles bursting on the surface is quiet loud.

the way i understand oxygen exchange works in our aquariums is that when the surface of the water is broken by the bubbles its allows the exchange of C02 and O2 gases from the tank to the atmosphere and, respectively, vise versa. the bubbles that travel through the water column from the air stone to the surface are essentially doing nothing besides slightly moving water around. its only when the bubbles burst on the surface is gaseous exchange taking place.

im thinking about removing the air all together and using wave-makers to agitate the surface of the water rather then bubble from an aerator. the surface will be agitated quiet aggressively similar to that seen in most marine aquariums.

my question is would the agitation from the wave-makers reduce the surface tension enough to allow for sufficient gaseous exchange to occur similar to that of my current aerator would be creating?

[malawi sand diver]

Hi Michael

The wavemaker should be fine provided there is lots of movement at the top of the water where the gas exchange happens. In addition to this, you can tweak your filter return to create some surface movement. e.g. I have a T pipe a couple of cm below the surface on my return which agitates the water without noise. I also have a wavemaker at one end of the tank about 10cm below the surface.

I did away with my aerator a while back and all is fine. Having good flow with the wavemaker will help the fish pump the oxygenated water past the gills. Plants can also slightly add to the disolved oxygen levels if you want to add those.

Regards, Rob

[gillsysyd]

There is a minute amount of transfer of oxygen in the bubbles rising to the surface, however not enough to make any different. It's all on the surface agitation.

Oxygen does get exchanged when the surface isn't being disturbed, however what the air stone/power head etc are doing is moving water from different areas of the tank to the surface to exchange out the co2 and absorb oxgyen.

What it is also doing is increasing the surface area, as a agitated surface has more surface area than a flat surface. What this is also doing is breaking up the oil that tends to form on the surface of still water, this is natural oils out of the atmosphere and can create a 'seal' on the surface of the water causing no exchange of gases as the surface. And that's one of the main reasons for agitation of the surface not just water circulation.