Hey- I read on another website today that air stones, etc. don't really add oxygen to the water becuase the bubbles aren't in contact with the water long enough.
This doesn't ring true to me, because even though the individual bubbles aren't in contact with the water very long, there is a constant stream of many bubbles in the water. However, I'm new at this and the web-site otherwise seemed well-informed.
Just wondering what y'all thought on the subject?
Full Version: Air Stones And Air Pumps
The air bubbles from an air pump oxygenate the water in several ways. The main way they work is, as the bubbles rise, they bring water from the bottom of the tank to the surface. When the water is exposed to the air at the surface, it picks up oxygen. The constant turnover of the water makes sure that the maximum amount of water is exposed to the surface.
The second way the bubbles work is that the surface area of the bubbles do inpart a small amount of oxygen to the water. The smaller the bubble, the more surface area of air bubble is in contact with the water and the more oxygen is imparted to the water.
Air bubbles are great -they turn over the water, they oxygenate, they look good, and the fish love playing in them.
The second way the bubbles work is that the surface area of the bubbles do inpart a small amount of oxygen to the water. The smaller the bubble, the more surface area of air bubble is in contact with the water and the more oxygen is imparted to the water.
Air bubbles are great -they turn over the water, they oxygenate, they look good, and the fish love playing in them.
That's interesting about the size of the bubbles and the smaller bubbles being more efficient Daryl. My bubble stone/wand makes big bubbles, maybe I'd be better off with smaller bubbles -but how would you know the size of the bubbles that are going to be produced when you're out shopping for a bubble pump?
The oxygenating ability of air stones and their respective bubbles is not related to the time in contact with water (from the bottom of the tank to the top) it is better understood by realizing the surface agitation that an air stone creates.
Oxygen is not very good at dissolving in water. At 100% saturation, in ideal water, oxygen is at 10ppm. For comparisons sake some people who keep planted freshwater tanks can have upwards of 50-100ppm of CO2 dissolved in their water column. CO2 (along with other gasses) is much better at dissolving in water than oxygen.
The surface agitation (the bubbles popping at the water surface) creates extra surface area for gas exchange between water and air.
Air stones also add circulation to the tank. As a bubble moves to the surface it is creating turbulent flow in the water around it. A following bubble does the same. The net effect is that water from near the area of the air stone is lifted to the top of the tank. Typically this lower water is less saturated with oxygen and more saturated with pollutants. Water near the surface of the tank is always more saturated with oxygen because of its proximity to the atmosphere. (You may have seen fish that hang out near the surface, they hang out there because the dissolved oxygen levels are higher and it is easier for them to "breathe".) The result is more water being exposed to higher oxygen concentrations. Thus, better oxygenated water circulating throughout the tank (which is essentially what you orginally expected the air stone and air pump to do !!!)
It is very hard to say whether or not there is actual gas exchange between the air in the rising bubble and the water. It seems logical that there is some exchange but I would think it all depends on the amount of time the bubble takes to rise from bottom to top.
Regardless, the greatest oxygenating ability comes from the combined effects of surface agitation (more gas exchange with atmosphere) and circulation (mixing of lower and higher oxygen saturated water) that the air stone creates. In addition any other toxic gases that may be in the water will eventually be released at the surface as well.
Kevin
Oxygen is not very good at dissolving in water. At 100% saturation, in ideal water, oxygen is at 10ppm. For comparisons sake some people who keep planted freshwater tanks can have upwards of 50-100ppm of CO2 dissolved in their water column. CO2 (along with other gasses) is much better at dissolving in water than oxygen.
The surface agitation (the bubbles popping at the water surface) creates extra surface area for gas exchange between water and air.
Air stones also add circulation to the tank. As a bubble moves to the surface it is creating turbulent flow in the water around it. A following bubble does the same. The net effect is that water from near the area of the air stone is lifted to the top of the tank. Typically this lower water is less saturated with oxygen and more saturated with pollutants. Water near the surface of the tank is always more saturated with oxygen because of its proximity to the atmosphere. (You may have seen fish that hang out near the surface, they hang out there because the dissolved oxygen levels are higher and it is easier for them to "breathe".) The result is more water being exposed to higher oxygen concentrations. Thus, better oxygenated water circulating throughout the tank (which is essentially what you orginally expected the air stone and air pump to do !!!)
It is very hard to say whether or not there is actual gas exchange between the air in the rising bubble and the water. It seems logical that there is some exchange but I would think it all depends on the amount of time the bubble takes to rise from bottom to top.
Regardless, the greatest oxygenating ability comes from the combined effects of surface agitation (more gas exchange with atmosphere) and circulation (mixing of lower and higher oxygen saturated water) that the air stone creates. In addition any other toxic gases that may be in the water will eventually be released at the surface as well.
Kevin
Trinket,
If you have a wand that is NOT made from stone you can actually take a safety pin/thumb tack/sewing needle and poke more holes into the wand to create more bubbles. Of course the smaller the hole you poke the smaller the bubble will be.
If you have a wand made of stone (usually a dark blue or darker green color with a very rough surface) you cannot poke more holes in it. However, you could soak it in a vinegar bath (make sure to rinse thouroughly before putting back in the tank) to see if you could open it up a little more.
Kevin
If you have a wand that is NOT made from stone you can actually take a safety pin/thumb tack/sewing needle and poke more holes into the wand to create more bubbles. Of course the smaller the hole you poke the smaller the bubble will be.
If you have a wand made of stone (usually a dark blue or darker green color with a very rough surface) you cannot poke more holes in it. However, you could soak it in a vinegar bath (make sure to rinse thouroughly before putting back in the tank) to see if you could open it up a little more.
Kevin
WOW greykmb !! you sounded like you were giving a Science Lesson with both of those posts. . . and for that you deserve a 
sticker ... 
.... very informative a very good read ..... 
Useful for me to as I was thinking to go out and get one tomorrow actually! THANKS!
sticker ... .... very informative a very good read ..... Useful for me to as I was thinking to go out and get one tomorrow actually! THANKS!
Great explanation! It was very useful.
I had always read that the bubbles didn't really add oxygen, but did promote the circulation by breaking the surface. I just never knew why and always wondered
Thanks!
I had always read that the bubbles didn't really add oxygen, but did promote the circulation by breaking the surface. I just never knew why and always wondered
Thanks!
Well- based on the response, I guess I better get me an air stone! Thanks for the info.
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