danilada Posted September 22, 2012 Report Share Posted September 22, 2012 Over the past few weeks I have been loosing a few guppies, water is perfect and is a very mature tank, so I am thinking I may not have enough air in the tank. I am looking to replace my old air pump anyway so how would I work out how much air a minute I am needing to pump through air stones? Quote Link to comment Share on other sites More sharing options...
livingart Posted September 22, 2012 Report Share Posted September 22, 2012 the air stones don't put much "air" in the tank, they do create flow which helps with gas exchange Quote Link to comment Share on other sites More sharing options...
Ira Posted September 22, 2012 Report Share Posted September 22, 2012 Generally if they not swimming around at the top of the tank gasping for air then you have enough. More circulation never hurts though. Quote Link to comment Share on other sites More sharing options...
GrahamC Posted September 22, 2012 Report Share Posted September 22, 2012 Oxygenation occurs at the surface of the water which is why the surface area of the water is used to calculate the carrying capacity of the tank. The air bubblers just breaks up the water surface which increases the oxygen exchange at the surface. Quote Link to comment Share on other sites More sharing options...
alanmin4304 Posted September 22, 2012 Report Share Posted September 22, 2012 The air bubbles increase the surface area. Just be careful in a power outage. Quote Link to comment Share on other sites More sharing options...
amtiskaw Posted September 23, 2012 Report Share Posted September 23, 2012 Oxygenation occurs at the surface of the water which is why the surface area of the water is used to calculate the carrying capacity of the tank. The air bubblers just breaks up the water surface which increases the oxygen exchange at the surface. I disagree. The surface area of the bubbles would far exceed the area of the tank's surface, so gas exchange is increased directly. Quote Link to comment Share on other sites More sharing options...
F15hguy Posted September 23, 2012 Report Share Posted September 23, 2012 gas exchange does occur within the bubbles, but the surface of the tank far exceeds the bubbles for the gas exchange due to the fact the air is also constantly refreshing itself, that is why you get almost the same amount of as exchange from a powerhead breaking the surface than as from an airstone. if gas exchange did not occur in the bubbles then the CO2 systems would have a bit of trouble Quote Link to comment Share on other sites More sharing options...
alanmin4304 Posted September 23, 2012 Report Share Posted September 23, 2012 That is why you need very small bubbles---because it is not easy to get the CO2 into the water. Water has a greater affinity for O2 than CO2 and that is why you can drive the CO2 out of water with aeration ( can be used to treat potable water supplies with CO2 problems) Quote Link to comment Share on other sites More sharing options...
GrahamC Posted September 23, 2012 Report Share Posted September 23, 2012 Oxygenation apparently occurs mostly when the air bubble is formed, and a miniscule amount occurs as the bubble rises to the surface. The EPA define bubble size as coarse and fine. Fine is less than 2 mm. And more efficient oxygenation occurs with fine bubbles. I've seen those fine bubblers on youtube but never seen them in shops so I think they must be experimental or just not in mass production. Coarse bubbles have most of their effect on water oxygenation by destratifying the water and moving deoxygenated water to the surface. As mentioned above a power head has the same effect, and a HOB waterfall filter perhaps even more so as the falling water can shear the larger bubbles formed at the surface into smaller ones which are then pushed below the surface. PS: air stones need to be replaced every couple of months or cleaned as they rapidly clog up with dust pulled out of the air. Quote Link to comment Share on other sites More sharing options...
F15hguy Posted September 24, 2012 Report Share Posted September 24, 2012 the air curtain design should put out mirco bubbles, also the flexible airstones (when clean) do a very fine bubble, and the ceramic variety claim 1-2mm bubbles smaller bubbles also move slower increasing contact time. btw airstones can be cleaned easily by boiling for a few seconds. Quote Link to comment Share on other sites More sharing options...
GrahamC Posted September 24, 2012 Report Share Posted September 24, 2012 I had this continuous water change system setup where I was siphoning water using an air stone at the source end, and it eventually blocked up. Tried boiling and it made no difference. had to toss it. The air stone was there so if the water level dropped below the level of the air stone, the siphon would not break. Quote Link to comment Share on other sites More sharing options...
Ira Posted September 24, 2012 Report Share Posted September 24, 2012 The air stone was there so if the water level dropped below the level of the air stone, the siphon would not break. Seems like it'd be easier to just put a U at both ends. Quote Link to comment Share on other sites More sharing options...
GrahamC Posted September 24, 2012 Report Share Posted September 24, 2012 And that would allow the siphon to restart once the water level rose? ( my water source was several feet higher than the tank ) Quote Link to comment Share on other sites More sharing options...
F15hguy Posted September 24, 2012 Report Share Posted September 24, 2012 should be able to scrape the outside of the stone, they don't often block on the inside (although it does happen RARELY) also had a few faulty new stones recently. people!! Blow through your airstone before leaving the store!!!!! Quote Link to comment Share on other sites More sharing options...
Ira Posted September 24, 2012 Report Share Posted September 24, 2012 And that would allow the siphon to restart once the water level rose? ( my water source was several feet higher than the tank ) Ah, ok I see what you're saying. No, wouldn't work, would only work if you could have the inlet and outlet at the same height. Quote Link to comment Share on other sites More sharing options...
David R Posted September 24, 2012 Report Share Posted September 24, 2012 Worth reading on this subject; http://www.tfhmagazine.com/aquarium-bas ... nation.htm Quote Link to comment Share on other sites More sharing options...
GrahamC Posted September 24, 2012 Report Share Posted September 24, 2012 Interesting, I thought piping is what Scottish ladies did with cakes. Quote Link to comment Share on other sites More sharing options...
amtiskaw Posted September 24, 2012 Report Share Posted September 24, 2012 gas exchange does occur within the bubbles, but the surface of the tank far exceeds the bubbles for the gas exchange due to the fact the air is also constantly refreshing itself, that is why you get almost the same amount of as exchange from a powerhead breaking the surface than as from an airstone. Any chance you can link to some research that proves this? I don't get your refreshing comment, sorry. I wouldn't have thought each bubble's going to exhaust it's O2 exchanging capacity in the few seconds it's submersed? Quote Link to comment Share on other sites More sharing options...
F15hguy Posted September 24, 2012 Report Share Posted September 24, 2012 its not but when the O2 content is higher (and CO2 lower) it will transfer a lot quicker, i.e. if the air was very high in CO2 then CO2 is going to be absorbed until the concentrations are more equal and virtually no O2 would be absorbed Quote Link to comment Share on other sites More sharing options...
GrahamC Posted September 24, 2012 Report Share Posted September 24, 2012 Maybe someone can google a reference on the rate of oxygen dissolution in a pressurized air bubble but I suspect it's not very quick. If you look at a planted tank you see lots of bubbles of pure oxygen being formed, and they seem to stick around for quite a while. Quote Link to comment Share on other sites More sharing options...
amtiskaw Posted September 25, 2012 Report Share Posted September 25, 2012 its not but when the O2 content is higher (and CO2 lower) it will transfer a lot quicker, i.e. if the air was very high in CO2 then CO2 is going to be absorbed until the concentrations are more equal and virtually no O2 would be absorbed Agreed, but you've lost me again - I don't see what that has to do with what we're discussing? The air pumping through your airstone is the same as the air at the surface of the tank. I'd imagine the surface area of all the bubbles combined greatly exceeds the area of the tank's surface, therefore the gas exchange of a bubbler exceeds the gas exchange at the tank's surface surface, and the benefit is direct gas exchange by the bubbles, not just increased surface agitation. Maybe someone can google a reference on the rate of oxygen dissolution in a pressurized air bubble but I suspect it's not very quick. If you look at a planted tank you see lots of bubbles of pure oxygen being formed, and they seem to stick around for quite a while. Vaguely recalling high school physics, I'd have thought you'd get more gas dissolving into water if bubbles are at a higher pressure than ambient atmospheric pressure? But then I don't think bubbles would be at a higher pressure in just a meter or so of water anyhow. BTW, sorry to the OP for the hijack :oops: Quote Link to comment Share on other sites More sharing options...
GrahamC Posted September 25, 2012 Report Share Posted September 25, 2012 Vaguely recalling high school physics, I'd have thought you'd get more gas dissolving into water if bubbles are at a higher pressure than ambient atmospheric pressure? But then I don't think bubbles would be at a higher pressure in just a meter or so of water anyhow. BTW, sorry to the OP for the hijack :oops: If the bubbles were not at a higher pressure than the surrounding water, they could not form right? I've kept my eye on an O2 bubble formed a few hours ago in my planted tank .. it's still there. Quote Link to comment Share on other sites More sharing options...
amtiskaw Posted September 25, 2012 Report Share Posted September 25, 2012 Bubbles displace water as they form, but they're basically at the same pressure as the air outside the water is what I'm saying. If they were formed in deep water they'd be at a higher pressure than the same volume of air at the surface, but the change in pressure in a few feet of water is negligible. Quote Link to comment Share on other sites More sharing options...
Ira Posted September 25, 2012 Report Share Posted September 25, 2012 Bubbles displace water as they form, but they're basically at the same pressure as the air outside the water is what I'm saying. Not really, same pressure as the water, but that will only the same as the outside air at the surface of the tank. If they were formed in deep water they'd be at a higher pressure than the same volume of air at the surface, but the change in pressure in a few feet of water is negligible. About half a PSI per foot, atmospheric pressure is roughly 14 PSI. So, roughly 1 PSI at the bottom of a 2 foot/600mm tank. So, yeah less than 10%, not really significant. Quote Link to comment Share on other sites More sharing options...
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