Surface Agitation vs Air Stones

[amtiskaw]

Browsing various fish keeping web sites and forums, including this one, I keep seeing people saying that surface agitation provides more dissolved oxygen than an air stone does. To me, this seems like a basic science fail, and is more like lore that people see and keep repeating without thinking about it.

If you consider that the surface area of a sphere is 4*Pi*R2 then a 1cm bubble adds 3.14 cm2. Multiply that by the number of bubbles and you soon start to see the huge amount of extra surface area bubbles add for gas exchange. Have a play with this surface area calculator and see what you think.

Yet fish keepers have no issues with getting as many bubbles as possible when using CO2 for planted aquariums. In this context, suddenly getting as many bubbles as possible is good as you get more dissolved CO2. So why is this different to getting oxygen via bubbles?

I did a quick search on this, and the best description I found to back my opinion was this guy's page. There were tons of sites saying the opposite, but none with any explanation, just statements with no reasoning provided.

What do you guys think, am I missing something and full of it? Feel free to show me the error of my ways. My ultimate fantasy is this will be the start of a groundswell of Interweb discussion that will rise up and slay this myth once and for all!

[disgustipated]

i remember this.. viewtopic.php?f=10&t=62688

i agree that surface agitation can help aerate the water but an air pump is far more effective considering it does both - air bubbles that dissolve into the water and surface agitation.

[smidey]

Are you saying that an air stone is better for surface agitation or that an air stone works better because the bubbles in the tank?

I have run my tanks all three different ways at various times. Surface agitation only, air stone with no additional surface agitation and both air stone and deliberate surface agitation. I do not understand the scienceon thus specific topic but what I do know is that there was no difference in any of the fish or water parameters that I could tell with either way of doing it. What I do know is that if I didn't do any of it then I quickly have gasping fish.

Which ever way you choose to do it you simply need enough of it to serve your needs but they all work to aerate the water.

Air stones aren't the be all and end all of achieving aeration, I have used my canister spray bar or a wave maker to do the job perfectly so just as much credit had to go to surface agitation as air bubbles floating to thesurface I think.

Unless I have missed something, the page you linked to are just that persons opinion on it and why he thinks that which is fair enough, personally I agree with it mostly being generated by surface agitation as I'm yet to find an air stone in the ocean so that theory works for me

[livingart]

There is more dissolved oxygen in my tanks with flow pumps and good surface movement than the ones with just airstones, if i increase the air through the stone or use wooden stones there is more DO. but then a lid is needed to contain the water from bubbles breaking and salt creep.

[Ira]

And water pumps to disturb the surface are far quieter than annoying loud as hell buzzy irritating, vibrating airpumps. :an!gry

[disgustipated]

the thread i linked to i was told literally "An airpump does not add oxygen to the tank" and that air bubbles coming from a pump do absolutely nothing to help aerate a tank, aside from the surface agitation that they create, and i disagreed.

in my large american cichlid tank, i had plenty of surface agitation from the two filter outlet hoses splashing in from above the surface, but the fish were still gasping at the surface, until i added an air pump and bubble wall, now they are breathing easy. i also note that the air pump is much, much quieter than having my filters create surface agitation, that was quite loud, lots of splashing and whatnot

[Ira]

much quieter than having my filters create surface agitation, that was quite loud, lots of splashing and whatnot

You don't need to have splashing, just turning over the surface and rippling is all you need. That should be practically silent.

[disgustipated]

yea i understand that, but am saying that rippling the surface was not enough, fish were gasping, made them splash more, fish still gasping. added air pump/stone and everything hunky dory. the air pump is doing more than i could get surface agitation to do...

[smidey]

yea i understand that, but am saying that rippling the surface was not enough, fish were gasping, made them splash more, fish still gasping. added air pump/stone and everything hunky dory. the air pump is doing more than i could get surface agitation to do...

i have experienced the opposite

[livingart]

never had a gasping fish in my cichlid tanks and never an airstone either

[camtang]

I have, but a quick adjustment of spray bar or water mover has always fixed it for me.

After reading several threads on here I removed my airpump set ups and played with my movement directions and have not looked back since.

I only think bubble are good as a decoration in a tank rather than a life support unit.

[smidey]

I have, but a quick adjustment of spray bar or water mover has always fixed it for me.

After reading several threads on here I removed my airpump set ups and played with my movement directions and have not looked back since.

I only think bubble are good as a decoration in a tank rather than a life support unit.

Just be careful relying on spray bars, I was doing that and the pipe came loose off the spray bar and stopped assisting the surface and made the tank oxygen deficient. I use both spray bar and bubbles but not a fan of the way the bubbles look

[camtang]

I had the opposit when my spry bar came loose, it flew out of the tank and did a water change onto the carpet for me.

[flymike]

Air stones simply use the bubbles to lift a column of water to the surface for gas exchange, the actual bubbles do very little to "aerate" the water.

A common term for using a small pump to move water to the surface is fluming, all you need is a slight disruption to the surface for it to work,

you also need to remember that the warmer the water the lower the dissolved oxygen levels get.

I have successfully grown tomatoes in a deep water culture (basically roots growing in a bucket of water) hydroponic system, using only fluming for aeration. The key is to keep the temps down around 18C, as the temps go up the dissolved oxygen goes down.

I found a good article on a koi pond site, cant seam to find it now though

From the research I've done, a waterfall type setup works best, with water cascading down in to the tank,

I think the idea is that the water comes in more contact with vertical and horizontal air movement for better gas exchange

[smidey]

Air stones simply use the bubbles to lift a column of water to the surface for gas exchange, the actual bubbles do very little to "aerate" the water.

A common term for using a small pump to move water to the surface is fluming, all you need is a slight disruption to the surface for it to work,

you also need to remember that the warmer the water the lower the dissolved oxygen levels get.

that's the theory the he is saying is wrong based on the other guys theory.

[livingart]

Tropical marine, sump, 25c, flow pumps 145% D.O.

4 x Air stones and heaps of air 105%

[disgustipated]

i think individual experiences here depend on the stocking of the tank.

my big tank is heavily stocked with big fish, it needs the airstone because making enough surface movement with filters is too splishy splashy.

my lightly stocked planted tank on the other hand - don't need an airstone in there, even slight surface movement from the filter keeps DO levels replenished.

i wonder why co2 bubbles are effective in adding co2 to the water, when oxygen bubbles are not effective?

[smidey]

my tanks are always heavily stocked african soup and the surface agitation via pump or spray bar was plenty.

[alanmin4304]

CO2 is added to tanks via a diffuser which gives off millions of tiny bubbles to help with disolving it or by other methods of doing the same thing. The air bubbles from an airstone are much larger so there is less total surface area to react with the water. There will of course be some oxygen go into solution from an airstone but I suspect most is from the atmosphere at the surface as the surface area is increased considerably. The airstone will

also be flushing spent gasses from the top of the tank so the atmoshere will remain fresher.

Conclusion: Both ways must be ideal. When you first go into a heavily stocked breeding room or quarantine room it is obvious from the smell that there is a lot of waste gasses produced by the fish. Most people I know in this situation will leave the door open for a while to give a complete air change. It does not take a lot of heat to rewarm the air, particularly if you have a large heatsink in the form of many litres of water.

[flymike]

i wonder why co2 bubbles are effective in adding co2 to the water, when oxygen bubbles are not effective?

Maybe if you ran pure oxygen through a defuser it may be different, I'm not sure, don't know allot about co2 or defusers

The actual surface area in contact with the bubbles them selves is very small.

You have to think about a running stream, and how much water disruption is happening, you have the friction along the edges and bottom slowing water on the outsides causing turbulence, and a simple rock or log in the middle will force flow up and around it, displacing water. The fish then selves cause turbulence in the water, I read an article once about the water movement caused by schooling pilchard or mackerel, each fish is only capable of putting a very small amount of energy in the water with its tail, but times that by millions and it turns out to be quite allot. (a little off track I know)

The surface area of the water is related to the amount of gas exchange possible, by placing a small pump on the bottom pointing up, lightly fluming the surface (only a small disruption, not a massive turbulent mess), you increase the surface to air ratio per hour.

An air-lift style pump will do the same thing (which is just an air stone type column of water directed up a tube)

I have used a return pipe on the bottom directed at the surface, and had great results, you are able to see small particles being pulled in to the column of water and lifted to the top.

I do understand both air stones and pumps will achieve the same thing at the end of the day, but some like the look and sound of bubbles, and some don't.

I guess power consumption may come in to it as well, I think the average air pump runs on less watts than your average power head.