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when i first got in to the hobby and discovered air pumps and what not but they did not make sense to me. how would blowing bubbles in water actualy put more air in water if they just float to the surface and pop? but everybody said it worked so i didnt question it but recently i discovered article about the same thing. it said the only way to get more air in water is surface agitation which bubblers do little.

Last edited by resle at 11-Apr-2005 15:55

From what I understand, it's a little more complicated than that. Fish need dissolved oxygen in the water, because that where they draw it from for respiration. Air stones and bubble curtains help to add more dissolved oxygen to the water, in two ways. One, some of the oxygen from the bubbles actually enters the water while the bubbles rise to the surface. Also, when they actually hit the surface, they agitate it. This surface movement helps to enhance gas exchange between the air and the water, which means that more oxygen can enter the water.

I think that's all correct. Hopefully this will make it clearer for you.

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And when he gets to Heaven, to Saint Peter he will tell: "One more Marine reporting, Sir! I've served my time in Hell."

As the article stated, oxygen transfer is primarily accomplished at the surface through agitation or movement of same. The air stones cause this surface agitation and/or movement thus assisting in the transfer of oxygen into the water.

Jim

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Water, taken in moderation, cannot hurt anybody. -- Mark Twain

If you have a HOB style filter that creates a splash into the tank and you're not seriously overstocked you'll be fine without an airstone. Planted tanks often minimize the ammount of surface agitation if they're injecting CO2 as the agitation will also drive off the CO2 that's being put in for the plants. The plants will make up for this by oxygenating the water for the fish.

^_^


[hr width='40%']"I'm alright, I'm alright
It only hurts when I breathe"

The air bubbles cause a current of water to move up, thus causing a movement of water across the surface as it moves up to the surface. This is where the air exchange takes place, at the surface of the water. Through defusion from a high gradient of O2 or CO2, it exchanges here at the surface. Without movement, the only gradient would be the water that is in full contact with the surface, and that which is not in contact, would become saturated, mostly/usually with CO2 (as the fish would use up all the O2).

As for the actual bubbles doing anything for air exchange, they do not. Or at least it is too small for measuring. The reason is, they move up too quickly, and thus do not have the time to desolve O2 into the water. This is also true of CO2 bubblers that just release bubbles, and do not use a diffuser or ladder. With a diffuser or ladder, the bubbles stay in the water longer, and thus have a chance to exchange CO2 into it.

HTH....

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