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How much aeration is too much?

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FISHnLAB

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Ontario, Canada
Hi guys, I have always ran air stones in my tanks(low tech) but, have recently been wondering if one can overdue it?

I generally run air stones pretty low, to keep noise at bay, and run fine bubble ones in all of my tanks now along with good surface agitation from my filter outputs just as kind of a one-two gas exchange punch if you will. I have noticed, with these fine bubble ones, that I now get much more microbubbles carried in the current around the tank(especially if placed near filter output) and that the amount can be adjusted by pump/air stone output similar to CO2 on high tech tanks. This got me to thinking about if in a worst case scenario one could overdo it or maybe even cause gas bubble disease in some of their livestock?

So, what do you guys think? How does one determine the right amount of aeration? How much is too much? Are there any dangers or is it just an aesthetic thing(ie too many ugly bubbles in my tank😂)?

Thanks for the input guys👍.
 
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I would say you would really have to apply a lot of aeration to hit a level where the amount of dissolved oxygen becomes a problem for the fish. Running an air stone is a good idea, but not essential if you have plenty of plants and good surface agitation and a reasonable stocking level. Some opt to run an air stone outside the photoperiod where plants consume oxygen to make sure the tank won't get too low on dissolved oxygen.

Cheers,
Michael
 
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FISHnLAB said:
This got me to thinking about if in a worst case scenario one could overdo it or maybe even cause gas bubble disease in some of their livestock?
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Someone correct me if I'm wrong, but my understanding is that this isn't possible. Gas bubble disease occurs when the water is supersaturated, that means pushed beyond it's natural state at equilibrium. When you run an air stone, all it is doing is creating bubbles that pop at the surface, breaking the surface tension and allowing gas exchange. The gas will not supersaturate under these conditions, it will equalise.

Think of a can of carbonated soda - when you open it, it immediately starts fizzing with co2 bubbles. These bubbles are trying to escape because it is supersaturated. If you put a fish into a tank with an equivalent saturation of oxygen, then you may be in danger, but not by an air bubbler.
 
xZaiox said:
Someone correct me if I'm wrong, but my understanding is that this isn't possible. Gas bubble disease occurs when the water is supersaturated, that means pushed beyond it's natural state at equilibrium. When you run an air stone, all it is doing is creating bubbles that pop at the surface, breaking the surface tension and allowing gas exchange. The gas will not supersaturate under these conditions, it will equalise.

Think of a can of carbonated soda - when you open it, it immediately starts fizzing with co2 bubbles. These bubbles are trying to escape because it is supersaturated. If you put a fish into a tank with an equivalent saturation of oxygen, then you may be in danger, but not by an air bubbler.
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Yes, I would consider it unlikely in a healthy aquatic environment. Certain conditions can cause O2 super saturation: https://www.waterboards.ca.gov/water_issues/programs/swamp/docs/cwt/guidance/3110en.pdf
"Water can be supersaturated with oxygen under certain conditions (e.g. when algae are growing rapidly and producing oxygen more quickly than it can be used up or released to the atmosphere"

Super saturation would be above 100% saturation level. When looking at the table (temp, DO mg/L), given the temperature ranges we normally are concerned about, I would find it exceedingly unlikely to reach O2 levels that could endanger our livestock even at slight super saturated levels. While hyperoxygenation may be possible it's not something I've ever encountered myself or heard of from anyone else who have experienced it in their aquarium, but I am all ears to learn what others have to say. I would say though, if your injecting CO2 you might possibly get into trouble with CO2 being displaced by O2, if you run heavy aeration during the day, but that's of course more of a plant consideration.

👍 to @FISHnLAB for asking the question.

Cheers,
Michael
 
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FISHnLAB said:
How does one determine the right amount of aeration?
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...3D modelling software and rigorous empirical investigation.
I have <thus far> failed to correctly assign saliency to air stones, except as a suitable alternative method of surface water agitation... but I do feel sometimes that they have some measure of intrinsic value. Perhaps I should approach Tetra to fund an academic project? ~~Tetra if you are reading this, yes, I would love to help :) - just PM me.
 
Hi all,
FISHnLAB said:
I have noticed, with these fine bubble ones, that I now get much more microbubbles carried in the current around the tank(especially if placed near filter output) and that the amount can be adjusted by pump/air stone output similar to CO2 on high tech tanks. This got me to thinking about if in a worst case scenario one could overdo it or maybe even cause gas bubble disease in some of their livestock?
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You can't really over-do it and fine bubbles are exactly <"what you want">.

Air is <"only 21% oxygen">, which is why it is almost impossible to <"super-saturate the water column with oxygen"> purely by adding air. If you could? Every waterfall would be accompanied by a lot of dead fish.

cc4-1.jpg


There <"are circumstances"> where oxygen (nearly always <"derived from photosynthesis">) can cause gas bubble disease, but it is pretty unlikely in our tanks.
dw1305 said:
I had an interesting one today. I won't tell you the location, or context, but it was a pond and the water sample had a dissolved oxygen level of 180% (~20oC, 18mg/L DO) and a pH value of pH 10.5...........
When we sealed the water collection bottles (collected with a <"Phil sampler">) the green water algae were pearling very noticeably. The water, and sweep net samples, are in the lab. at the moment, so I will eventually have some invertebrate numbers and chlorophyll, NO3, NH3 and PO4 values.

The pH and supersaturation of oxygen were both caused by the phytoplankton bloom, and the total lack of water movement.
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cheers Darrel
 
I don't think that fine mist is necessarily what we want. Although surface area and residence time are parameters that benefit the gas exchange, turbulence at the surface is also fundamental. When the bubbles are so small that they just "go with the flow", they don't offer resistance to the water and don't cause turbulence. When a larger bubble floats from the bottom of the tank all the way to the surface, it creates the micro-turbulence on its surface and effectively dissolve part of its content into the water. That's why it wiggles a little bit and doesn't just go straight up.

There is, then, an optimal bubble size, where the surface area and the residence time are increased, but there is still turbulence.

Saying that air bubbles don't contribute to dissolving oxygen sounds very weird to me, since that's how the simple CO2 diffusers work and we know they work. Oxygen and CO2 may have different solubility, but the overall idea is the same. That's why I think those diffusers forming a mist of micro CO2 bubbles don't really help all that much (other than possibly depositing the bubbles at the plant surface), and sometimes you get a very polluted tank and still can't increase CO2 dissolution.
 
Hi all,
LMuhlen said:
Although surface area and residence time are parameters that benefit the gas exchange, turbulence at the surface is also fundamental. When the bubbles are so small that they just "go with the flow", they don't offer resistance to the water and don't cause turbulence.
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<"Turbulence is good">, laminar flow is even better. Basically it is all about <"maximising the gas exchange surface area">, it doesn't really matter how you get there.
LMuhlen said:
Saying that air bubbles don't contribute to dissolving oxygen sounds very weird to me
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The advantage of the <"small bubbles"> is actually that they do dissolve in the water column, so you get "direct aeration", rather than "indirect aeration".

Personally I <"like belt and braces">, so I have <"laminar flow">, <"turbulence and small bubbles">, although all of them are probably largely irrelevant in tanks with low BOD and plenty of plants.

Have a look at <"https://plecoplanet.com/pleco/aeration-and-dissolved-oxygen-in-the-aquarium/">, I wrote it a long time ago but it is still relevant.

There is a bit of a discussion about <"very small bubbles"> in one of our Twinstar threads <"Twinstar..what is it?">.

cheers Darrel
 
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dw1305 said:
Hi all,

<"Turbulence is good">, laminar flow is even better. Basically it is all about <"maximising the gas exchange surface area">, it doesn't really matter how you get there.

The advantage of the <"small bubbles"> is actually that they do dissolve in the water column, so you get "direct aeration", rather than "indirect aeration".

Personally I <"like belt and braces">, so I have <"laminar flow">, <"turbulence and small bubbles">, although all of them are probably largely irrelevant in tanks with low BOD and plenty of plants.

Have a look at <"https://plecoplanet.com/pleco/aeration-and-dissolved-oxygen-in-the-aquarium/">, I wrote it a long time ago but it is still relevant.

There is a bit of a discussion about <"very small bubbles"> in one of our Twinstar threads <"Twinstar..what is it?">.

cheers Darrel
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Hey Darrel, your PlecoPlanet link isn't working. I would like to read it if there is another link? Thanks for your contributions, they are very helpful as usual👍.
 
dw1305 said:
<"Turbulence is good">, laminar flow is even better. Basically it is all about <"maximising the gas exchange surface area">, it doesn't really matter how you get there.
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When I say turbulent flow, it is not the flow pattern in the tank as a whole, it is the turbulence formed in the micro region around the bubble, really at the gas-liquid interface. Micro-turbulence. It is analogous to convective heat exchange.

It is possible to watch it with the CO2 bubbles. Using a simple diffuser, the bubbles are formed a little larger and they float really fast, zig-zagging a bit. After a moment, closer to the surface, they are smaller and slower, since part of the CO2 dissolved. They zig-zag less. If enough CO2 manages to dissolve before reaching the surface, the bubble gets so small that it stops floating up and goes with the flow. At this point, there is so little gas left in the bubble, most of it already dissolved, that you would think that it would disappear at any moment, but instead they keep existing and following the laminar current of the tank "forever", or until they adhere to something or get dragged into the filter or reach the surface. That's because there is not enough turbulence at the interface and the dissolution happens really slowly.
 
Mines on the same timer as the lights. Seems to work ok. I see a bit of a film on the surface of the water but it’s gone a bit later once the pump comes on.
I followed the don’t throttle the airstone principle but use a bleed instead. This stops putting too much back pressure on the Air Pump and seems to be working well at the moment.
 
Simon Cole said:
That's precisely it. I doubt we will ever know in our lifetimes whether these air stones have very much impact if there is already good water circulation
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Hi @Simon Cole

Although the ORP/Redox of my tank water is +370 to +380 mV, I suspect that this may increase a tad if an airstone was added to the tank. Who knows? But I could give it a try. I do know the difference between dissolved oxygen (a gas) and ORP/Redox (oxidizers and reducers) - the simplified version. Or, I could just measure dissolved oxygen.

If I can find the time, I'll check it out.

JPC
 
@jaypeecee - :thumbup: Measurements should be most observable at maximum depth.

"Significant death rates occur when dissolved oxygen remains above 115%-120% air saturation for a period of time. Total mortality occurs in young salmon and trout in under three days at 120% dissolved oxygen saturation" <a dubious source>.
@dw1305 found 180% dissolved oxygen in a pond once. It is kind-of bonkers when you think about it, because pearling does in my experience correlate strongly to lethargic behaviour in fish when I am really pushing my carbon dioxide injection rates in my planted aquariums at home. Do other people observe this? So potentially livestock have to put up with a pH drop, elevated carbon dioxide, and elevated oxygen levels. It is no wonder livestock deaths are so common. Given the toxicity of oxygen as opposed to carbon dioxide, I do wonder whether livestock wipe-outs more a result of elevated oxygen levels.
 
Simon Cole said:
...pearling does in my experience correlate strongly to lethargic behaviour in fish when I am really pushing my carbon dioxide injection rates in my planted aquariums...
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Hi @Simon Cole & Everyone,

From the above, could one not conclude that the fishes' behaviour is simply the result of excessive carbon dioxide in the water? Or, what am I overlooking?

JPC
 
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