Maximizing An Air Pump's Air Contribution

Homeslice

Aren't like 99% of all air pumps have a vast majority of their work go to waste? Like, the oxygen floats to the top, a little dissolving in the water along the way, but quickly leaves the water. Would something like what I sketched out more fully utilize an air pump's capacity?

An air pump air hose goes into the tank. It connects to a T connection, out the other two inlets go 2 more air hoses. One just sits somewhere in the tank so that water can be sucked in. The other is a very long air hose that wraps around something over and over and over again, so that the air and water have to travel through a looooooooooong hose. During all that time traveling air is dissolved into the water.

I guess you would have fully maximized your air pump if the very last oxygen bubble dissolves into the water a split second before the water leaves the hose - so you would not even see oxygen bubbles coming out!

Anything wrong with this?

Thanks!


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jjohnwm

You're not pumping oxygen into your tank, it's just plain old atmospheric air. The water is usually close to saturated with all the dissolved oxygen, carbon dioxide, etc that it can hold. Beyond that point no more will dissolve. Even if all the oxygen dissolved into the water, that air is something like 70% nitrogen. You will never ever see the bubbles just "disappear" before they reach the surface.

Even if the water in the tank were able to dissolve significantly more oxygen than it already held, the air bubbles in the long tube would only be exposed to the tiny amount of water in the tube, which would be quickly saturated long before it reached the end of the tube. After that, it's just bubbles in a tube.
 

aae0130

The air does not dissolve into the water. It’s only purpose is to rise and break the surface of the water. You can take advantage of the electrical energy spent to run the pump by adding an air driven sponge filter to the tank or use the air to drive an under gravel filter system. That’s it in the nut shell.
 

Homeslice

You're not pumping oxygen into your tank, it's just plain old atmospheric air. The water is usually close to saturated with all the dissolved oxygen, carbon dioxide, etc that it can hold. Beyond that point no more will dissolve. Even if all the oxygen dissolved into the water, that air is something like 70% nitrogen. You will never ever see the bubbles just "disappear" before they reach the surface.

Even if the water in the tank were able to dissolve significantly more oxygen than it already held, the air bubbles in the long tube would only be exposed to the tiny amount of water in the tube, which would be quickly saturated long before it reached the end of the tube. After that, it's just bubbles in a tube.


All excellent points jjohnwm, thanks.
 

Homeslice

The air does not dissolve into the water. It’s only purpose is to rise and break the surface of the water. You can take advantage of the electrical energy spent to run the pump by adding an air driven sponge filter to the tank or use the air to drive an under gravel filter system. That’s it in the nut shell.



Thanks aae0130. How do you know its only purpose is to rise and break the surface of the water? I thought someone had posted a study awhile back that showed something close to the opposite, that it was the air being dissolved into the water as it came up that provided the most oxygen.
 

aae0130

Think about it this way.
What is water? It’s H2O. The O is for oxygen. If you were to change the number of oxygen in the water, it would no longer be water.
The air bubbles rise in the water and break the surface tension, allowing gases to escape. Some of the gases are from the nitrogen cycle and some are the result of reactions in the tank chemistry. The water and air molecules are not binding with one another and creating something.
 

JayH

You could use some of the same techniques employed for getting CO2 into the water. The more time the air spends under the water, the more of it that will be absorbed into the water. Also, surface area plays a very big part as that's where the mixing of water and gas takes place. The smaller the bubbles coming out of the air stone, the more gas will work its way into the water. One single 3mm diameter bubble can form over 27,000 of 0.1mm diameter that collectively have 30 times the surface area of the single 3mm bubble. Unfortunately, to get those kinds of bubbles you need gas under high pressure going through a high quality diffuser.

You can increase the contact time by lengthening the trip to the surface. Get a tube and wrap air hose tightly around the outside, most of the way up the tube, gluing it in place. Now slide that assembly into another hollow tube that seals fairly tightly against the air hose. Plug both ends of the air hose. Air injected between the two tubes now has to travel around and around between the wraps of air hose. The exact length of the path will depend on the diameter and length of the tubes, but even at smaller diameters it's many times the length of the direct path.

All that said, this is largely a wasted effort. Efficiency of oxygen transfer into the water is not huge deal. Air is cheap. Just pump in more if you don't think the water is oxygenated sufficiently. Get a giant bubble wand or a bunch of air stones or a few very good quality sponge filters. Concern about efficiency is best reserved for resources that are expensive or scarce.
 

JayH

Think about it this way.
What is water? It’s H2O. The O is for oxygen. If you were to change the number of oxygen in the water, it would no longer be water.
It doesn't work that way. If this were true, you couldn't dissolve ANYTHING in water without it no longer being water. All those aquascapers putting CO2 into their water would be changing the water itself.

Water actually has the capacity to hold incredible amounts of dissolved gases, including oxygen. Fish are not breaking apart water molecules when they breathe. They're extracting gaseous oxygen from the water.
 

aae0130

Believe me, the air bubbles from the pump are not dissolving into the water. They are rising out of the water and breaking the surface tension, allowing other gases to escape with them when they do. That’s it.......
 

JayH

Believe me, the air bubbles from the pump are not dissolving into the water. They are rising out of the water and breaking the surface tension, allowing other gases to escape with them when they do. That’s it.......
I'm afraid your claim that oxygen can't dissolve into water without it no longer being water has made it clearly unwise to simply accept what you say on the topic as proven fact. If you can provide references to research backing up your contention I'm sure we'd all be extremely interested. Until then, I'm going to assume air bubbles in an aquarium behave just like any other gas bubbles in water, with gas molecules from the surface of the bubble going into solution in the water.

There is little question that most of the air from a typical air stone rises to the top of the aquarium and escapes into the atmosphere without going into solution in the water. There is also little question that some of the air does go into solution. A few weeks ago someone linked to a scientific paper stating that more oxygen got into the water directly from the bubbles than from surface agitation. Barring reference to research showing the opposite, I'm inclined to believe that paper.
 

JayH

I have been reading stuff like this for years....
Is an Air Pump Necessary for a Fish Tank? | Fishkeeping Planet

Can you please post a resource?
The question here is not whether the fish will have insufficient oxygen without air bubbles. The question was about maximizing the oxygen in the water and getting the most out of an air pump. The claim that air bubbles do not contribute oxygen to the water is simply false. If it was true, all those people pumping CO2 into their tanks for the plants would be wasting a lot of money because those CO2 bubbles wouldn't be dissolving into the water.

Oxygen from the air bubbles is being dissolved into the water. Clearly not all of it. Not even a majority of it. But some is.The amount is going to depend on a lot of factors, including the size of the bubbles, the depth of the tank, the temperature of the water, and the level of oxygen already in the water.

In most cases I would agree that the oxygen added to the water directly from the bubbles is probably not significant, but that's completely different than, "The air does not dissolve into the water."

This paper doesn't apply directly since it deals with nano-bubbles much smaller than anyone is likely to generate in an aquarium, but I believe some of the basic principles involved would still apply. For those who don't care to follow the link, they tested the effect of high oxygen levels due to injection of oxygen nano-bubbles on hydroponic plants, sweetfish and trout, and mice (who I assumed were given the water to drink). They found substantial additional weight gain for the fish kept in the nano-bubble water. It seems reasonable to assume that higher oxygen levels in the water are good for the fish, so whatever can be done to increase those levels is a good thing.

I don't know that nano-bubbles would be practical in the average home aquarium, but it would be interesting to see experiments with CO2 injection equipment running with O2 rather than CO2. I'd love to see a comparison of health and growth rate of similar fish kept in normally aerated tanks and in O2-injected tanks.
 

aae0130

I understand that water can hold a limited amount of dissolved oxygen. The problem is that an aquarium environment with filtration and exposure to the atmosphere is already fully oxygenated. If you could increase this (impossible) you would be changing the water at a molecular level.

good luck getting nanobubbles in your aquarium. If you can do it, it will probably get you a Nobel prize.
 

JayH

I understand that water can hold a limited amount of dissolved oxygen. The problem is that an aquarium environment with filtration and exposure to the atmosphere is already fully oxygenated. If you could increase this (impossible) you would be changing the water at a molecular level.
Are we back to this? Adding gaseous oxygen to water is NOT going to change the water at a molecular level. One of the reasons water is so universal is the water molecule is chemically stable. Simply forcing more oxygen gas into the water is not going to change it to H2O2. To make H2O2 you have to split the hydrogen and oxygen and then recombine them. This requires a lot of energy, not just the presence of gaseous oxygen.

What we consider properly oxygenated aquarium water has in the range of 6-7ppm oxygen. This is about 2ppm below the normal level for natural bodies of water. It should be possible to get 7.5-8.5ppm oxygen in the home aquarium without going to extraordinary efforts. In the nano-bubble experiments they were able to push the oxygenation to 30ppm. So there's a lot of room between "normal" and the limits of what can be done at atmospheric pressure.

It would be wise to also note that "normal" oxygen levels will go up as water temperature drops and go down as water temperature rises. If you raise the aquarium temperature to help the fish fight infection, it might be a good idea to do what you can to increase the oxygen levels. They're already struggling and can only benefit from not having to push more water through their gills to get more oxygen.
 

JayH

Anyone interested in methods of increasing the dissolved oxygen level should watch this video He evaluates several filtration/aeration scenarios in the same tank to show the differences in oxygen level.


TLDW: 1) Duckweed, or any floating plant, is the enemy of oxygenation. If it covers most of the water surface the oxygen level is going to suffer to a significant extent. 2) An air stone or conventional sponge filter will increase oxygenation by about 0.5ppm even if you have a canister filter outlet heavily rippling the water surface.
 

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