Air bubbles

[Miguel]

except that surface tension does not have any effect on gas transfer. If you have a film (pond scum) on your surface that will effect gas transfer, but the actual surface tension of the water will not.

Ok. I thought surface tension was an obstacle to the exchange of gases...and that is why I like the bubbles, because, by breaking the tension on the surface, they promoted the gas exchange...

been living ( I won't say for 30 plus years because as baby hobbyist i couldn't care less ) but for 20 years with this "mistake"

Also like the way you "think"

 

[Miguel]

Most oxygen transfer happends at the waters surface, this is due to the rippling effect caused when the bubbles hit the surface.
A powerhead pointed towards the surface is a better option the an airstoneas the actual bubbles from an airstone do little in the way of adding oxygen whilst in the water column. Instead, as stated, it is the extra surface area due to the rippling water which adds the bulk of oxygen.
So if you have a powerhead pointed upwards, the wave effect caused by the powerhead at the waters surface is more benifical then an airstone.

Nova, you're right about the power head imo. In terms of gas exchange you may be doing the same conceptual mistake I am, acording to "Ituffwhatchamacallit ". According to him, and it makes logic to me, you have gas exchange inside the water column, ( as opposed to the surface, happening on the interface of the bubbles "surface" and the water..

 

[Nova 8]

Ok. I thought surface tension was an obstacle to the exchange of gases...and that is why I like the bubbles, because, by breaking the tension on the surface, they promoted the gas exchange...

been living ( I won't say for 30 plus years because as baby hobbyist i couldn't care less ) but for 20 years with this "mistake"

Also like the way you "think"

You are correct in thinking that it is at the water surface where most of the oxygen exchange happens, but your wording is incorrect. Water tension has nothing to do with it, it is surface area which does the most work.

 

[Nova 8]

Nova, you're right about the power head imo. In terms of gas exchange you may be doing the same conceptual mistake I am, acording to "Ituffwhatchamacallit ". According to him, and it makes logic to me, you have gas exchange inside the water column, ( as opposed to the surface, happening on the interface of the bubbles "surface" and the water..

Nope, I have read airbubbles do not stay in the water column long enough, nore do they hold enough oxygen to compare with a larger water surface. Not only that but agetating (sp) the surface helps expel gases. I am not mistaken. How do you think the ocean receives it oxygen, through a giant bubble coloumn or through surface area.

 

[Nova 8]

Found this;

Dissolved OxygenObviously, fish need oxygen to breath. But so do bacteria, and even plants, at night, require oxygen. Well oxygenated water is the halmark of a healthy aquarium. Since warm water, like that in all tropical fish aquariums, holds less oxygen than cold water, it is a challenge to keep the dissolved oxygen concentration high. Oxygen gets into the water at the suface, where the water is in contact with the air. The best way to promote gas exchange is to provide some gentle agitation of the suface, either with the filter outflow, a small water pump. Airstones also help, but they are not as efficient as surface agitation. It also helps to keep the oxygen demand low. Overstocked aquariums will obviously have a high oxygen demand, but there are larger sources of oxygen demand that are often not well known. Aquariums with an overabundance of uneaten food and rotting debris always have high oxygen demand (and low dissolved oxygen concentration) due to the huge populations of decomposers. Feeding lightly and understocking will go a long way toward maintaining a high dissolved oxygen concentration. Signs of oxygen stress in aquarium fish include rapid gill movements, gasping, and hanging out near the water surface where the oxygen concentration is higher. If you see fish displaying any of these behaviors do a water change immediately and provide aggressive surface agitation.

 

[Miguel]

You're right and that last article is perfectly correct. I always said that surface agitation is a must ( gas exchange in the water column in the bubbles surface, this I learnt today in this thread ).

My mistake, admittedly ( and english is not my language, so bear with me), was that water tension needed to be broken ( which i did via surface agitation ) it being an impediment, an obstacle to gas exchange.

 

[Nova 8]

Thats good, if you think something is true stick to ya guns unless they show proof. Also water tension is extremely hard to break (if possible at all) as even rippling wter still retains tension, gases is not effect by tension. Sure you wont be able to rest a pin on rippling water but if you hit it hard the force you'd feel would be the tension, if it had no tension it would be like air.

 

[IITUFFTOBEATII]

Nope, I have read airbubbles do not stay in the water column long enough, nore do they hold enough oxygen to compare with a larger water surface. Not only that but agetating (sp) the surface helps expel gases. I am not mistaken. How do you think the ocean receives it oxygen, through a giant bubble coloumn or through surface area.

I'm sorry but you have read wrong, again call any waste water treatment plant, or any plant that needs to oxygenate water to return it to a lake or stream, they all use bubbler sytems, in extreme cases the will use batch reactors that use misters, concept is the same however. Also the bubbles have the same concentration of oxygen as the atmosphere, about 21%

the fact that they are bubble does not matter, you are correct that its all about the surface area, bubbles increase surface area as they each have their own, added up its is quite significant

FACTS

 

[IITUFFTOBEATII]

Found this;

Dissolved OxygenObviously, fish need oxygen to breath. But so do bacteria, and even plants, at night, require oxygen. Well oxygenated water is the halmark of a healthy aquarium. Since warm water, like that in all tropical fish aquariums, holds less oxygen than cold water, it is a challenge to keep the dissolved oxygen concentration high. Oxygen gets into the water at the suface, where the water is in contact with the air. The best way to promote gas exchange is to provide some gentle agitation of the suface, either with the filter outflow, a small water pump. Airstones also help, but they are not as efficient as surface agitation. It also helps to keep the oxygen demand low. Overstocked aquariums will obviously have a high oxygen demand, but there are larger sources of oxygen demand that are often not well known. Aquariums with an overabundance of uneaten food and rotting debris always have high oxygen demand (and low dissolved oxygen concentration) due to the huge populations of decomposers. Feeding lightly and understocking will go a long way toward maintaining a high dissolved oxygen concentration. Signs of oxygen stress in aquarium fish include rapid gill movements, gasping, and hanging out near the water surface where the oxygen concentration is higher. If you see fish displaying any of these behaviors do a water change immediately and provide aggressive surface agitation.

This is incorrect, probably written by a hobbyist, airstones are hands down the best way to oxygenate water. I have done experiments in the lab to prove this, i can email you the results if you would like, its in an excel file.

surface agitation only displaces the oxygen rich boundary layer that is near the surface and causes it to mix with the less oxygenated water beneath.

 

[Nova 8]

Send me your studies because, as I said to miguel, I will not change my way of thought based just on word of mouth, facts have to be given. Even then I will still probably disagree with you. Who are you to say that just cause you think someone is a hobbiest that they are wrong due to the fact that you have done scientific studies, whats to say that other people with contradicting results haven't done lab tests.
Science is always getting something wrong at one point or another, just look at how many time a fish gets in scientific names changed. There is always contradicting evidence misproving someone elses test or theroey. So it is very likely that your test are infact incorrect. I have read more article supporting my view then your view, in books, magazines and on the internet. Actually, it is usually the newer hobbiest that states that airstones are the best way to add oxygen to the water (it would be if you were pumping pure oxygen).

I would still like to read your study, I'm sure it will be an interesting read.