Micro Scrubbing Bubbles.

[Randy Holmes-Farley]

If, theoretically nano bubbles were being produced, would there not eventually be so many tightly clumped together bubbles they become visible?

You mean before the tank theoretically contains more air than water and every fish lies on the bottom unable to float? I do not know. :D

 

[Waterjockey]

I'm not sure I understand the basis of your comments.

Are you suggesting the surface tension is deterring gas exchange across the air/water interface? If so, why do you think it? Why would it?

The surface area to volume ratio is going up as the bubble size decreases, so equilibration of a small bubble will be a lot faster than a large one. A 1 micron bubble should equilibrate 100 times faster than a 100 micron bubble, based just on the basis of the surface area to volume ratio. Of course there are other effects, but the ones I know of, such as slow diffusion to and from the air/water interface through the water, will make smaller bubbles seem even faster to equilibrate than large ones.

Also, the contact time is not necessarily especially short for small bubbles, and may be substantially longer than large bubbles.

Hi Randy.
I am aware that for a given volume of gas, smaller bubbles equate to more surface area..it also tends to equate to "stronger" bubbles.
The best way to describe what I meant is the bubbles "want" to hold thier shape, and are not easily dissolved at low system pressures and contact times in a typical home aquarium piping system......leading to my thoughts it would be unlikely to supersaturate any gasses in the tank resulting in harm to fish metabolism.
Think of gas reactors where for efficient gas exchange you want huge media surface area, very thin film fluids, high gas pressures and long contact time. To dissolve gasses in a fluid, bubbling is not a very efficient way to do it. I have experience with industrial daf (dissolved air floatation) systems, and what some are describing as "smoke" in the water is what we would generally refer to as microbubbles...not "nanobubbles", as you already mentioned in another reply, would not be directly visible to the naked eye. I'm semi-interested in the micro-bubble experiment as a flocculation device (or as others have put it, turning your whole tank into a skimmer for a few hours). The other claims I must admit I dismiss as........enthuisiasm by some.

On a side note, I imagine the "nanobubble" creation (if any) would occur at the sudden pressure drop at the piping outlet (discharge to tank point).

Cheers!

 

[Lasse]

Hi Lassie. I have a difficult time reconciling the idea that there will be any supersaturation of gasses in a home reef pumping system. (a) They are very low pressure systems. (b) Contact time is minimal. (c) It's bubbles, which don't diffuse into the water well...even if some believe they are getting micro bubbles. Surface area is small and tension is high. Surface area and pressure are key...think of very thin large surface areas, and contact time for efficient gas exchange. I doubt "microbubble" entrainment ina home aquarium does very much for dissolved gasses. I have been trying it for a week or so as an experiment to see if it acts as a detrius binder/carrier though, and there does appear to be some merit via skimate. I will have to try a few weeks with and without and document skimate production and quality to have a quantitative answer as apposed to ancedodal though. I start documenting tomorrow with no bubble entrainment and go from there.

Cheers

Hello Waterjockey

I really appreciate your posts - now we're talking essentials regarding the use of the technique in question.

a) “They are very low pressure systems.” This has been my major concern in order to “translate” my experiences from systems with pressure from 1 bar and upwards. Maybe you’re right but there are things talking against this too. I do not think that it is any problems with most of the impeller pumps that not exceed 3 – 4 m lifting height. However there is pumps on the market that manage 7 m and more and people start to talk about to use pumps with 3 bar (30 m lifting capacity). I do not really know the critical pressure for the saturation point of nitrogen gas under pressure in order to give an oversaturation in the open system (the tank/aquarium) of more than 101 – 103 %. Gas Bubble Disease (GBD) is known from open systems in the nature (1 atm) – as an example – downstream high waterfall and hydropower dams. I believe that it will not be an oversaturation of any gas just through contact between air and water in an open system (1 atm).

In the case of waterfalls – I believe that it’s the bubbles that will be transferred down into deeper water below the waterfall that deliver the gas for oversaturation.

Pressure rise with 0.1 bar per m water so my theory is as follow: - if the water is 10 meter deep below the waterfall and air will be transported down there as bubbles – you will have a saturation point of the gas determined by the pressure of 1 bar and the water that later will be transported up to the surface release excess gas as the pressure decreases. In this way an oversaturation of the gases that exist in air will be create. If the deep is 7 meter – you get a pressure of 0.7 bar and so on. This rise a question of what happens if you bubble microbubbles in deep tanks – any from the public aquaria scene that knows that?

Downstream hydropower dams – It is likely air that has been sucked in to the generators or temperature differences that create the oversaturation.

b) “Contact time is minimal.” I do not believe that the retention time is of large importance if the air will be inserted in the pipe system before the outlet. This because I know of own experiences that the opposite – releasing of the gases

occur at the sudden pressure drop at the piping outlet (discharge to tank point).

is more or less instantly.

In the case of introducing the air in a nozzle or diffusor just in the end of the pipe – I´m uncertain if the saturation pressure is high enough to create an oversaturation in the open tank. At the moment – I do not believe that.

However – if you elaborate with 3 bar pressure as our fellow down under will do – I´m a little bit concerned.

c) Gas exchange through bubbling compared with other methods. I will quote one earlier post about oxygen – it’s true for all gas exchanges but note – it either take away excess gases or put in gases if there are a shortfall of certain gases. It depends on the relationship between the concentration of the gas in the water and in the air - the equilibrium point

[QOTE="Lasse, post: 2849564, member: 66404"]For a normal aquarium - yes - the gas exchange happens when the popping bubbles reach the surface and create a large interface between the water and air.

But in sewage treatment plants - there is technics that create so small bubbles (not nano - but small) that because of their small size and the long residence times manage to oxygenate as good as surface movement (and better). Directly translated from Swedish – their name is membrane aerators. Do not know the English name. But this bubbles are injected rather deep (I was working with basins of 4 meters depth) Per meter – they gives around the same oxygen content to the water as you get per meter of a contra aerated Trickling filter.

Many years ago when the diffusers was new to the fresh water hobby – I did a test to see if they did what they should. I use three or four different brands (and pumps) placed 0.3 meter below the surface of a 40 cubic meters fish tank with treated waste water. The pumps did not created a larger interface between the air and the water and they was placed so it did not transfer the bottom water up to the surface. It was a lot of oxygen consumption in that tank. As soon I turn the inlet down – the oxygen level was going down.

To my surprise – one of them did what it says to do. Oxygen the water without disturbing the surface. There was the same oxygen level at the bottom as it was at the surface. And this was fresh water. The other three was not working the way it should.

So my conclusion is that if the bubbles is small enough (not nano size!) and the residence time is enough – they will oxygenate the water (or take away oxygen if the water is supersaturated). I believe that this happens all the time in the skimmer! See my graph in an earlier post there the oxygen content stabilizes around 90 % saturation during night.
[/QUOTE]

I´m sorry for long post but I love discussion like this. At least I am forced to rethink all my ideas- put them on paper in a foreign language and try to understand others argumentation. I develop my own thinking a lot and sometimes it strengths my ideas and sometime I´m forced to reject them.


Sincerely Lasse

 

[Waterjockey]

Hello Waterjockey

I really appreciate your posts - now we're talking essentials regarding the use of the technique in question.

a) “They are very low pressure systems.” This has been my major concern in order to “translate” my experiences from systems with pressure from 1 bar and upwards. Maybe you’re right but there are things talking against this too. I do not think that it is any problems with most of the impeller pumps that not exceed 3 – 4 m lifting height. However there is pumps on the market that manage 7 m and more and people start to talk about to use pumps with 3 bar (30 m lifting capacity). I do not really know the critical pressure for the saturation point of nitrogen gas under pressure in order to give an oversaturation in the open system (the tank/aquarium) of more than 101 – 103 %. Gas Bubble Disease (GBD) is known from open systems in the nature (1 atm) – as an example – downstream high waterfall and hydropower dams. I believe that it will not be an oversaturation of any gas just through contact between air and water in an open system (1 atm).

In the case of waterfalls – I believe that it’s the bubbles that will be transferred down into deeper water below the waterfall that deliver the gas for oversaturation.

Pressure rise with 0.1 bar per m water so my theory is as follow: - if the water is 10 meter deep below the waterfall and air will be transported down there as bubbles – you will have a saturation point of the gas determined by the pressure of 1 bar and the water that later will be transported up to the surface release excess gas as the pressure decreases. In this way an oversaturation of the gases that exist in air will be create. If the deep is 7 meter – you get a pressure of 0.7 bar and so on. This rise a question of what happens if you bubble microbubbles in deep tanks – any from the public aquaria scene that knows that?

Downstream hydropower dams – It is likely air that has been sucked in to the generators or temperature differences that create the oversaturation.

b) “Contact time is minimal.” I do not believe that the retention time is of large importance if the air will be inserted in the pipe system before the outlet. This because I know of own experiences that the opposite – releasing of the gases is more or less instantly.

In the case of introducing the air in a nozzle or diffusor just in the end of the pipe – I´m uncertain if the saturation pressure is high enough to create an oversaturation in the open tank. At the moment – I do not believe that.

However – if you elaborate with 3 bar pressure as our fellow down under will do – I´m a little bit concerned.

c) Gas exchange through bubbling compared with other methods. I will quote one earlier post about oxygen – it’s true for all gas exchanges but note – it either take away excess gases or put in gases if there are a shortfall of certain gases. It depends on the relationship between the concentration of the gas in the water and in the air - the equilibrium point

[QOTE="Lasse, post: 2849564, member: 66404"]For a normal aquarium - yes - the gas exchange happens when the popping bubbles reach the surface and create a large interface between the water and air.

But in sewage treatment plants - there is technics that create so small bubbles (not nano - but small) that because of their small size and the long residence times manage to oxygenate as good as surface movement (and better). Directly translated from Swedish – their name is membrane aerators. Do not know the English name. But this bubbles are injected rather deep (I was working with basins of 4 meters depth) Per meter – they gives around the same oxygen content to the water as you get per meter of a contra aerated Trickling filter.

Many years ago when the diffusers was new to the fresh water hobby – I did a test to see if they did what they should. I use three or four different brands (and pumps) placed 0.3 meter below the surface of a 40 cubic meters fish tank with treated waste water. The pumps did not created a larger interface between the air and the water and they was placed so it did not transfer the bottom water up to the surface. It was a lot of oxygen consumption in that tank. As soon I turn the inlet down – the oxygen level was going down.

To my surprise – one of them did what it says to do. Oxygen the water without disturbing the surface. There was the same oxygen level at the bottom as it was at the surface. And this was fresh water. The other three was not working the way it should.

So my conclusion is that if the bubbles is small enough (not nano size!) and the residence time is enough – they will oxygenate the water (or take away oxygen if the water is supersaturated). I believe that this happens all the time in the skimmer! See my graph in an earlier post there the oxygen content stabilizes around 90 % saturation during night.

I´m sorry for long post but I love discussion like this. At least I am forced to rethink all my ideas- put them on paper in a foreign language and try to understand others argumentation. I develop my own thinking a lot and sometimes it strengths my ideas and sometime I´m forced to reject them.


Sincerely Lasse[/QUOTE]

Hi Lasse,

You are doing a fine job with translating into a foreign language and getting your meaning across. I am enjoying the conversation, and I believe we are thinking along the same lines for the most part. I do not have the equipment at home to do any dissolved oxygen tests, and I am not really interested in the idea enough to spend that kind of money on the equipment for experimenting...so for me, until someone conclusively is able to demonstrate otherwise, I am stuck with my somewhat informed gut feeling. In hydro dams, the water undergoes a fairly quick compression as it travels down the penstock to the turbine. Some air is entrained in the water via the penstock vents. As it exits the turbine, the pressure is almost instantaniously returned to only a few meters water head pressure. (Turbine exit is not far below the dischage water surface). If you *see* a lot of air entrained at the exit from a power turbine, it was likely injected via compressors for either running in synchonous condensor mode, or sometimes to help with turbine vibrations at certain loads. On a non-air injected water turbine, there is not a lot of air (IMHO) given the massive volume of water exiting (sometimes hundreds of cubic meters of water per second, per turbine).

Cheers!

 

[Lasse]

I wrote generators - ment turbins :) However - injection of air before the turbines was new for me - but it explain a lot according to GBD down streams hydro dams.


Sincerely Lasse

 

[jedimasterben]

After a few more days (initial post here, day one update here), the detritus pile has not decreased any that I've noticed. I was not home nearly all this weekend, so I was unable to establish a new baseline for photos (sorry guys), but to the eye there is no noticeable change.

I love that I got a PM from someone stating that since I have a single place for detritus to settle, and not spread out throughout the rocks and other areas of the tank like most tanks, that my system has poor flow, and that the bubbles for some reason would not magically lift the detritus out of the tank like it would if said detritus were among the rocks. Made me LOL.

I have noticed, though, that the amount of bubbles that are 'sticking' under the rocks and such has decreased each night, which is strange to me on how exactly that would work. I'm still using the same air pump for the same amount of time in the same spot, haven't touched anything on the system except feeding it.


In my post-day one update I remarked that skimmate production had increased. What I hadn't remembered is that I started dosing lanthanum chloride prior to starting this, three drops (which will reduce phosphate by 0.0498ppm in my ~50g total system), so the increase in skimmate production can be attributed to that IMHO.

 

[Squamosa]

bubbles for some reason would not magically lift

That is rather silly, whoever first mentioned it :)

I wonder how the bubbles would do that, maybe if you stirred everything up and dispersed the detritus through the water column, like a cloud, you might have some of the lighter detritus being carried away to the skimmer by the bubbles, otherwise I think it just won't happen...just a thought :)

 

[jedimasterben]

That is rather silly, whoever first mentioned it :)

I wonder how the bubbles would do that, maybe if you stirred everything up and dispersed the detritus through the water column, like a cloud, you might have some of the lighter detritus being carried away to the skimmer by the bubbles, otherwise I think it just won't happen...just a thought :)

Is it really that silly? These quotes only come from this thread and not your separate thread in which the original post mentions the exact same thing. ;)

4. removal of detritus and floating particulates

The same effect described above happens (seems to lift detritus and causes the coras to slime).

Microbubbling has been our solution to keep the detritus from settling back down onto the rockwork we just cleaned.

Your skimmer does not remove detritus from the display tank.
Does not remove excess mucus and carry it to the sump...

Wait wait what ever goes through my sump comes in contact with my skimmer. So then you are saying that all the bubbles do is take the detritus to the sump ?

No sir... if that were the case, why is there detritus on your sandbed and rock work?

One thing I can say for certain is, the amount of detritus I have in my rock has greatly diminished in just two weeks of micro-scrubbing.

Though the nanobubbles themselves have minimal buoyancy, they still have buoyancy that adds up when grouped together on a piece of detritus.
This has a greater buoyancy and is more efficient at floatation than detritus surrounding an air bubble.
"As bubbles float up to the surface, they catch solids (contaminants) suspended in the liquid and bring them up to the surface. Since suspended solids are not uniform in size and shape, large bubbles often fail to catch and bring them up to the surface. On the other hand, micro/nano bubbles can penetrate into small dents of a contaminant and enclose it entirely in a ball of tiny bubbles, making it buoyant."

Below is a video of my tank bubbles, but I think that even at HD quality the video doesn't pick up the nano bubbles. But, as noted above, they do accumulate on detritus and other materiel in the tank and eventually bring it to the surface. I know this isn't long term and that the picture probably doesn't do it justice, but the water is quite clear.

If you had heavy detritus in your DT... how clogged would your system be and what would the overall health of the tank be congested with waste?
How do you think the tank's health is after enabling the detritus and stuck on organics and floating particulates are removed to the sump to be removed by the skimmer as a nutrient export?

4. removal of detritus and floating particulates

Addressing two known issues (Poor Ventilation and AERATION) and (DETRITUS REMOVAL from DT) solves a a lot of issues our friends in the hobby are seeing daily.

My tank has never been so clean, at least in terms of detritus. If I take a turkey baster and blow off the rock, nothing comes off...nothing. 20 fish and I feed twice a day.

 

[metrokat]

Haven't read the whole thread but I would think if there was detritus or whatever in the water column then the coral slime would attach to it which has bubbles attached to it, and then the wavemaker blows it about and eventually (hopefully) it gets filtered out. But unless the bubbles are the Rhoomba robot, it's not going to magically pick it up from the bottom of the tank. The bubbles hardly even go that far into the tank seeing as they are air they naturally do their best to escape upwards.

 

[jedimasterben]

Haven't read the whole thread but I would think if there was detritus or whatever in the water column then the coral slime would attach to it which has bubbles attached to it, and then the wavemaker blows it about and eventually (hopefully) it gets filtered out. But unless the bubbles are the Rhoomba robot, it's not going to magically pick it up from the bottom of the tank. The bubbles hardly even go that far into the tank seeing as they are air they naturally do their best to escape upwards.

If that were the case, the bubbles would not be able to find their way into the rocks of others' tanks at all, and there would also not be bubbles stuck under the rock that my detritus pile is under, about an inch and a half away ;)

 

[metrokat]

If that were the case, the bubbles would not be able to find their way into the rocks of others' tanks at all, and there would also not be bubbles stuck under the rock that my detritus pile is under, about an inch and a half away ;)

It's getting blown there by the powerhead, it's not magically getting there. The # of bubbles under the lower rocks is hardly any compared to the rest of the tank.

 

[jedimasterben]

I don't have any powerheads ;)

 

[MaccaPopEye]

@jedimasterben do you know how long it takes for a detritus pile of that size to build up? You could vacuum it out and see how long it takes to build back up. If it doesn't build back up then maybe the bubbling helps move it down to the sump it before it can find that sweet spot and settle? Or alternatively a quicker method would be to give that pile a good mix up a few minutes before bubbling is supposed to start one night and in a few days see if the pile is significantly smaller if there at all?

 

[jedimasterben]

@jedimasterben do you know how long it takes for a detritus pile of that size to build up? You could vacuum it out and see how long it takes to build back up. If it doesn't build back up then maybe the bubbling helps move it down to the sump it before it can find that sweet spot and settle? Or alternatively a quicker method would be to give that pile a good mix up a few minutes before bubbling is supposed to start one night and in a few days see if the pile is significantly smaller if there at all?

Last water change was March 6th, so it has taken since then for that to have built up, though I had recently stirred up some stuff in my sump and so some might have come from there.

Literally the only reason I'm a 'bubbler' :D is to test whether or not that facet of bubbling is true. If I am going to simply stir up that pile, then more than likely it will not be the bubbles getting rid of it or lessening it, it would be me stirring it up and getting it back into suspension. After the 'experiment' I believe I am going to get a Tunze 6020 to point at the starboard to keep everything moving a bit more.

 

[McMullen]

It seems if bubbling gets rid of cyano, it would alleviate at lest small/light detritus particles?! Perhaps not larger particles....but, cyano in my experience is thick and heavy compard to detritus blowing with turkey baster. What you think Jedi master?

 

[jedimasterben]

It seems if bubbling gets rid of cyano, it would alleviate at lest small/light detritus particles?! Perhaps not larger particles....but, cyano in my experience is thick and heavy compard to detritus blowing with turkey baster. What you think Jedi master?

Well, cyano is definitely a different beast altogether than detritus, but in theory if it works for cyano mats it should work for most everything, even sand lol.

 

[MaccaPopEye]

If I am going to simply stir up that pile, then more than likely it will not be the bubbles getting rid of it or lessening it, it would be me stirring it up and getting it back into suspension.

Yeah that's true, I doubt all of it would go down to the sump though just from being mixed up. Surely some would still find its way back into the same spot. Really my main point was to get rid of the detritus one way or another and see if it comes back over the next month or so while bubbling. If it doesn't come back over a similar or greater time period then it would be fair to say that the bubbling helps to prevent the detritus from settling in that spot by getting it before it settles and taking it down to the sump.

Although I do agree that in my experience cyano is fairly thick and heavy compared to detritus so if the claims about cyano are true then I would expect it to remove the detritus as well.

 

[jedimasterben]

Yeah that's true, I doubt all of it would go down to the sump though just from being mixed up. Surely some would still find its way back into the same spot. Really my main point was to get rid of the detritus one way or another and see if it comes back over the next month or so while bubbling. If it doesn't come back over a similar or greater time period then it would be fair to say that the bubbling helps to prevent the detritus from settling in that spot by getting it before it settles and taking it down to the sump.

Although I do agree that in my experience cyano is fairly thick and heavy compared to detritus so if the claims about cyano are true then I would expect it to remove the detritus as well.

I'm sure that it would eventually get taken out if I kept stirring it back up - but that's not quite what the claims are, and this is what I am testing :)

 

[Squamosa]

Is it really that silly? These quotes only come from this thread and not your separate thread in which the original post mentions the exact same thing. ;)

Who's being silly now? :p

 

[McMullen]

Detritus is an interesting test in my mind considering a couple people have posted bubbling is the only thing to rid the tank of cyano.

I believe them BTW, but if it works for one, should the other.