Air From Air Pump

[AdAndrews]

does the air coming out of an airpump into a tank do anything for the plants?

 

[shortymet55]

No, really its just agitating the water to get a bit more oxygen dissolved in the tank.

 

[AdAndrews]

No, really its just agitating the water to get a bit more oxygen dissolved in the tank.

ok, didnt think so, i was just thinking maybe some sort of c02 from what we breath out would be in the air, and therefore help the plants? or nitrogen in the air helping some how?.. no? ok

thanks

 

[Bignose]

The issue is that a bubble doesn't contain much gas, doesn't have very much surface area to diffuse gas into, and doesn't stay in the water for very long at. The combination of all three makes the resulting gas-exchange from a bubble completely insignificant versus the gas-exchange that occurs at the surface of the tank.

The bubbles do 2 small things, however. In that they agitate the surface of the tank when they get to the top and pop -- that agitation which affects the entire surface of the water increases the gas exchange over the entire surface. In addition, bubbles do cause circulation in the tank because of the water that they drag up to the top with them -- that brings water from the bottom of the tank to the top and vice versa. This keeps the entire tank well-mixed.

 

[AdAndrews]

The issue is that a bubble doesn't contain much gas, doesn't have very much surface area to diffuse gas into, and doesn't stay in the water for very long at. The combination of all three makes the resulting gas-exchange from a bubble completely insignificant versus the gas-exchange that occurs at the surface of the tank.

The bubbles do 2 small things, however. In that they agitate the surface of the tank when they get to the top and pop -- that agitation which affects the entire surface of the water increases the gas exchange over the entire surface. In addition, bubbles do cause circulation in the tank because of the water that they drag up to the top with them -- that brings water from the bottom of the tank to the top and vice versa. This keeps the entire tank well-mixed.

ok thanks for the help mate

 

[ChiNA MaN]

i heard the air stones/curtains drive off Co2 and causes plants to grow slower.

 

[Bignose]

i heard the air stones/curtains drive off Co2 and causes plants to grow slower.

Only true if you are putting extra CO2 into the water in the first place.

The bigger picture is that everything in nature tends toward equilibrium. If there is excess CO2 in the water, then it will tend to leave the water. If there is agitation at the surface, that increases the rate of mixing at the surface, which will make the system tend toward equilibrium faster. But, if there isn't excess CO2, then it won't drive it off, the same equilibrium will be maintained. And, if these is less than saturation levels of CO2, surface agitation will actually increase the amount of CO2 coming in because again of the increased mixing.

You have to include the condition of "excess CO2" for your statement to be true.

 

[three-fingers]

Aaaaaaaaaaaaand what is the equilibrium of CO2 in water?

I've seen 0.5ppm mentioned (all the other figures I've seen relate to the average amount of CO2 when it's not being injected, rather than the equilibrium level), so going by that it would seem that most aquariums do have an excess level of CO2 and that using an airpump would serve to help lower it back to 0.5ppm.

So surface agitation would be bad for plants unless your injecting CO2 to compensate.

Unless the equilibrium level is a lot higher than that.

 

[Bignose]

The equilibrium level is going to be highly temperature, pressure, and pH dependent, so a single value won't cut it. I actually don't have a resource at the moment for the values, but I will try to find one tonight/tomorrow and see what I can come up with.