# "Second Hand" Surface Agitation!



## mike L (22 May 2018)

I've ran air-stones at lights out, I've ran them 24/7 with co2 cranked up to compensate. The battle for good oxygen levels without de-gassing co2 always seems to take place at the water surface which recently led me to an idea/experiment. 

What if I create "another" surface which I can aerate as viciously as I like 24/7...and then feed this aerated water gently back into the water column?

I know some folks use a dedicated chamber in their sump to do this, but my tank configuration rules this out.

I do however have an available shelf above my tank, so I have used a little Eheim pump to take tank water into what resembles an overhead aquaponic type tray..minus any media or plants. This water is vigorously aerated..._and then some_. It goes back out via a bulkhead and is delivered at a nice easy pace into the tank's mid-water column, doubling as addition flow for co2 dispersal. 

I've basically just created another surface for my tank. The main surface remains like a crystal clear still-mill-pond thanks to my surface skimmer, and I make no demands whatsoever on it in terms of atmospheric oxygen absorption, which is now being entirely handled by my tank's "second" surface.

I basically figured: _" I'm injecting co2 into my water column via a reactor which exists outside the tank, why not make an *oxygen reactor,* which to some extent, vigorously agitated water continuously exposed to the atmosphere kind of is...is it not?"_

Anyway, the water clarity in my tank is off the charts, so that means my external filter is enjoying the oxygen boost, and my plants are loving the stable, rich co2 levels and are pearling away during the photo-period.

Most importantly though, my fish are looking really perky and healthy and don't go to the surface at all unless to feed. Which considering how "still" and un-agitated my surface is, I find the most amazing thing of all!!

I can co2 charge my water column AND oxygen charge it also without so much as a ripple on the surface.

I _was_ considering a wet-dry filter mounted overhead to achieve the same ends, but figured that just giving my external filter improved oxygen levels would be a satisfactory outcome.

Anyway, just wanted to share this with the community.

Although it's still a kind of prototype arrangement, I'll try get some pics up soon.

Cheers

Mike


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## sciencefiction (23 May 2018)

Anything that can increase oxygen levels is a good idea. Even the thought of increasing oxygen levels is a start in the right direction. I think many folks ignore the importance of that and take oxygen levels for granted.


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## Zeus. (23 May 2018)

Can't see it making much of a difference once the lights are on and plants are pearling as then the [O2] in the tank is saturated at about 10ppm. So extra surface agitation during the photoperiod will just increase the CO2 losses, running an airstone during the day increases the CO2 losses too. Having the extra at night will help O2 levels but simple airstone on timer can achieve that. Generally canisters better for CO2 tanks as they help reduce CO2 losses.
Fish at the surface isn't because of low O2 it's the [CO2] in the fishes blood that drives there breathing as it decreases the fishes blood pH which can get to toxic levels. Nothing to do with [O2].
So if it works for you great. But there will be very little benefit (if any) for your plants or fish increasing it further IMO. Airstone during non CO2/light periods only is plenty. During CO2//light period it is wasted.
As for more aerobic filtration, again no need in planted tank as our plants are the biggest filters in our tanks.
If you did what to increase gaseous exchange at the surface just have a fan blowing on surface will have the same effect as increasing surface area, but will increase CO2 loss again.


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## dw1305 (23 May 2018)

Hi all,





mike L said:


> I do however have an available shelf above my tank, so I have used a little Eheim pump to take tank water into what resembles an overhead aquaponic type tray..minus any media or plants. This water is vigorously aerated..._and then some_. It goes back out via a bulkhead and is delivered at a nice easy pace into the tank's mid-water column, doubling as addition flow for co2 dispersal.


That should work pretty well at night to increase oxygen levels. 





Zeus. said:


> Can't see it making much of a difference once the lights are on and plants are pearling as then the [O2] in the tank is saturated at about 10ppm.


This is true, once you have pearling you know the tank water is super-saturated with oxygen.

This is one of the advantages of plants (that is often over-looked on non-plant orientated forums), is that air is ~21% oxygen (O2), but photosynthesis produces 100% oxygen, and is a <"net oxygen producer">. Plants produced the <"oxygen we breathe">, and the fossil fuel we burn.

The other factor that people often ignore is that the internal tissues, and air spaces, of the plant are also fully saturated with oxygen at the end of the photo-period, and this oxygen is used for respiration by the plant during the non-photo period. Diana Walstad says: (on page 6. of  <"Ecology of the Planted Aquarium">





> ..... Even when plants are not photosynthesizing, such as night, they probably remove much less oxygen than one would expect. This is because they prefer oxygen stored in their tissues rather than take up oxygen from the water.
> 
> During photosynthesis, oxygen accumulates rapidly within the plant lacunae, which are huge gas storage areas making up about 70% of the plant's interior. This internal oxygen is used for the plant's respiration both day and night.....





Zeus. said:


> Fish at the surface isn't because of low O2 it's the [CO2] in the fishes blood that drives there breathing as it decreases the fishes blood pH which can get to toxic levels. Nothing to do with [O2].


This has come up a few times, but without a definitive answer.

I'm not a CO2 user, but if I was, fish at the tank surface would be a clear indicator that you have too much dissolved CO2. Haemoglobin transports both oxygen and CO2, which diffuse in and out of the blood along their <"diffusion gradients at the gill/water interface">. The pH changes in the blood are due to the higher levels of H2CO3 at enhanced CO2 levels (<"Bohr and Root effects">). Tom Barr (@plantbrain) observed that you could have higher CO2 levels in tanks with a greater level of oxygenation, but I can't find the thread (it may not be on UKAPS).





Zeus. said:


> As for more aerobic filtration, again no need in planted tank as our plants are the biggest filters in our tanks.


Plants are just the magic goose that lays the golden egg.

cheers Darrel


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## Zeus. (23 May 2018)

dw1305 said:


> This has come up a few times, but without a definitive answer.



My understanding comes from having studied the physiology of humans respiration not fish, but they are our distance ancestors so think it will be the same
But seeing the nerve supply of the head and neck of humans is based around the evolutionary development of the fishes phyangeal archs to man, which in the grand expand of time didn't take long.

 The respiration process is basically the same in fishes and man ie though water, it's just man carries his water with him, so the control centers are probably very similar in both. ie plasma pH drives respiration, with the blood plasma being the main transport media for CO2.

Carbon Monoxide (CO) affinty (bonding) to heamagoblin is x350 that of CO2 so when CO bonds to heamagoblin it stays bonded unlike CO2. When all the heamagoblin is boned in the blood no O2 transport takes place. Tissues don't get O2 anaerobic respiration at the tissue takes place for short time but limited capacity for this in humans. O2 levels drop to levels that can't support the tissues, CO2 levels don't increase as no O2 to feed the respiration at tissue level and the plasma is still removing any CO2 produced via the lungs and no decrease in blood pH so no increase in breathing rate. Time passed we fall asleep and die painleassly. I assume same for fish they would die without gasping at the surface of we used CO in tank.


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## dw1305 (23 May 2018)

Hi all,





Zeus. said:


> My understanding comes from having studied the physiology of humans respiration not fish, but they are our distance ancestors so think it will be the same But seeing the nerve supply of the head and neck of humans is based around the evolutionary development of the fishes phyangeal archs to man, which in the grand expand of time didn't take long.


I'm sure they are the same, slightly off topic but if any-one is interested in this area of evolution <"Your inner fish"> by Neil Shubin is a good, and accessible, read.





Zeus. said:


> The respiration process is basically the same in fishes and man ie though water, it's just man carries his water with him, so the control centers are probably very similar in both. ie plasma pH drives respiration, with the blood plasma being the main transport media for CO2.


I think the differences in fish are in the linked <"Respiration in fish"> pages about the <"Root Effect">.

cheers Darrel


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## ian_m (23 May 2018)

I thought there was a lot of research done, years ago with radioactively label oxygen, and it found most of the O2 in a fish tank actually came from the water surface rather then any aeration from an air pump. This was due to increased contact time with water surface allowing O2 dissolve as opposed to the brief contact time with aeration bubbles.


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## Zeus. (23 May 2018)

ian_m said:


> I thought there was a lot of research done, years ago with radioactively label oxygen, and it found most of the O2 in a fish tank actually came from the water surface rather then any aeration from an air pump. This was due to increased contact time with water surface allowing O2 dissolve as opposed to the brief contact time with aeration bubbles.



Dunno! I base my understanding on the gills on fish evolved into lungs and water is needed as a transport medium for the CO2/O2 to pass from the atmosphere to the blood in both. I would assume it claims the O2 in the bubbles didn't contribute much to the O2 in the water it came mainly form the atomsphere which makes sense in a way as the bubbling water increases surface agitation so increase surface area.


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## Barbara Turner (23 May 2018)

An alternative solution might be to buy a Chihiros Algae Doctor, I'm still not convinced about whether it does everything else it claims to.  
but it definitely does a good job at creating a super fine mist of oxygen with minimal surface agitation.


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## Zeus. (23 May 2018)

Reading on from one of Darrel's links read 
*Hypoxia in fish* which does surgested fish do have O2 sensors in the gills mainly, this hypothesis is also surported by fish also have behavior changes when [O2] is low eg darting and swimming near surface. It does mention O2 sensors in mammals in the carotid artery, but not much evidence to support them as low [O2] is rare in land mammals which with diffusion being 10,000 faster in air than water is no surprise. I would hypothesis the carotid sensors in mammals are the evolutionary remains of the O2 sensors found in fish gills. Just like the appendix in humans.


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