Aeration and Bubble Size

[LongTime]

I found the following statement at this site: http://www.keepalive.net/guide.htm.

"SIZE AND AMOUNT OF AIR BUBBLES

Take a look at at the air bubbles produced by an aquarium aerator. Watch how quickly the bubbles rise to the surface. They provide little aeration, but are aesthetically pleasing to watch. Bubbles must remain contacting the water, if they are to do the job properly. A good rule of thumb is: The smaller the bubble, the longer it will remain suspended in water to dissolve."

Has something changed or is this just someone trying to sell a product? I learned a "LongTime" ago that airstones do not force air into the water but the size of a standard airstone was designed to bring the water to the surface where oxygenation occured.

Did I miss an update along the line?

By the way, I got into this doing research to help a friend keep gizzard shad alive.

 

[Red Tailed Wonder]

isnt that 4 livewells that fisherman use?

 

[LongTime]

Yes, the product is for livewells but I am still became interested in the bubble size question.

 

[webcricket]

Like you said, as far as I know bubble wands and such are just a decorative way to increase surface agitation and through that achieve better oxygenation. If the filter moves enough surface water they aren't even necessary. Oxygen exchange takes place at the surface of the tank, not with floating bubbles in the tank.

 

[Rbishop]

So how does the water, around a bubble, know it is not in contact with air from the surface vice air in the bubble?

 

[misopeenut]

Oxygen exchange takes place at the surface of the tank, not with floating bubbles in the tank.

so i dont have to put a diffuser in the water to put co2 in my tank?
i can just have the tube blow co2 right above the surface.
:huh:

i think the size of the bubble matters.
just like co2, you dont want big bubbles, you want small bubbles so that it has more time to dissolve in water
correct?

 

[phanmc]

The majority of the oxygen in tanks are derived from the water surface. The agitation is necessary to break the water tension to allow better gas exchange. Additional oxygen infusion is usually unnecessary if given enough surface agitation.

In the situations that extra oxygenation is required then yes, smaller bubbles is better than larger bubbles because by breaking the oxygen bubble into smaller bubbles, you provide a larger surface area between the oxygen and water (same concept for CO2 injection).

 

[webcricket]

Okay, I guess I should have said "most" of the oxygenation occurs at the surface. : The fact still remains that if you have adequate surface agitation from your filter that air stones/wands/whatever are not necessary and serve a decorative purpose only...however...

Co2 diffusers are a whole other matter for planted tanks and I will claim to know nothing about that since I prefer plastic plants. I just assumed we were talking about regular aeration devices that create bubbles, not co2 diffusers.

 

[LongTime]

Thanks for the discussion. I found it quite interesting.