# Equal co2 distribution



## nigel bentley (18 Feb 2021)

Hi, 
Thought I had good Co2 distribution having a nice light green on drop checker when situated in middle of tank. However, with experimenting as you do? I have found a dead spot back left corner 
Drop checker is green but quite dark. I have two questions Is this a major issue and if so can I rectify it? The tank is a1500mm long 100gallon 20" deep. I have spray bars running along the length of back wall. 1/3 of those point upwards for surface agitation, the rest point down at 45 degrees. The Co2 diffuser is on the back wall to the right. I also have an Eheim air circulator on right wall. Sorry for the long winded text, any advice would be much appreciated. Thanks. Nigel


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## aquascape1987 (19 Feb 2021)

I personally think that your problem is caused by your spray bars pointing in different directions to each other. Some are probably degrading/cancelling the effect of the flow of others. If it were me, I would  have all of your spray bars on the back wall, slightly below the water surface, pointing primarily forward, but with an EVER SO SLIGHT upward direction. Just enough to ripple the surface of the water, as the flow projects forwards out of them.

I think this way, you will have all the flow first causing a ripple of the surface for gas exchange, the momentum then carrying it forward until it hits the front glass, and then down to the substrate, and then back around across the bottom of your tank, completing the circle of flow back to the filter intakes. The general direction of flow from all of your spray bars will then be uniform, and augment each other, rather than working against each other.

If your spray bars cover the majority of the length of the back wall of the tank, and you have enough filter power feeding them, I think this should give you very good, and even flow around the majority of your aquarium.


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## ceg4048 (19 Feb 2021)

I agree fully with aquascape1987's assessment. While it _is_ possible, due to the layout of hardscape and plant mass, that pointing each bar at a different direction may work, typically we want as much water mass moving in the same direction. The momentum of the moving mass usually has a better chance of flowing in the direction we want. I see the same mistakes being made when folks have multiple pumps and they mount one pump on the left wall while the other is mounted on the right wall. The two flows which then are in opposite directions cancel each other out. Spraybar technique depends on coherency of the flow.

See the thread Water flow in the planted aquarium?

In any case, that is the first step, the baseline configuration, after which we can then deviate in order to find the best flow solution.

Cheers,


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## EA James (19 Feb 2021)

Hi all,

I've often thought about changing my filter outlet to a full length spray bar on my EA 1200 to better distribute nutrients equally around the tank but how does this affect the intake to the filter?
My intake is positioned on the bottom right of the tank so surely this means it's only taking in the same section of water as the flow is circulating in a different direction, would the opposite side be circulating 'dirty' water as it's over a metre away from the intake it won't have much chance of being pushed through the filter

Cheers, James


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## nigel bentley (19 Feb 2021)

Thanks so much for your relies, I will move the spray bars today. I have also noticed a kink in one of my out pipes. I will also sort this out. 

Thanks again Nigel


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## aquascape1987 (19 Feb 2021)

ceg4048 said:


> I agree fully with aquascape1987's assessment.


To be honest Clive, I developed my current  ideas on flow from experimenting with my own tanks, after taking pointers from many of your historic  posts on the forum, and  also your replies to my own flow problems years ago.




EA James said:


> I've often thought about changing my filter outlet to a full length spray bar on my EA 1200 to better distribute nutrients equally around the tank


I personally gave up using Lilly pipes in favour of this method about a year ago, and have never looked back since. I have found flow to be far superior using spray bars in this way, and my results with the plants and algae have proved this to me. I still use glass intake tubes though.

Although most people consider them an eyesore, and consider glass lilly pipes much more pleasing on the eye, I have found that I rarely see my black spray bars against my black background, due to them camouflaging in very well. Also because the angle the tank is viewed from,is 99 percent of the time from above, and not with your head on the same level as the tank (unless you bend down). Even the EA1200 is viewed from above unless you sit down in front of it. This means that the spray bars are completely concealed by the rippling mirror effect of the water surface when viewed even from slightly above. It looks like there is nothing there at all. I also find glass lillys to be sometimes just as much an eyesore, as they are large, strange shaped and more often than not, right at the front of the glass in your direct view. They aren’t invisible by any stretch of the imagination.




EA James said:


> My intake is positioned on the bottom right of the tank so surely this means it's only taking in the same section of water as the flow is circulating in a different direction, would the opposite side be circulating 'dirty' water as it's over a metre away from the intake it won't have much chance of being pushed through the filter



I’m not sure exactly what you mean here, but I think what you are saying is that your intake(s) are in the front bottom corners?
If so, I think the system would work better with the intakes in the corners, right below the spray bars, as you would do with a normal lilly pipe. Not exactly so sure it is because it means only ‘dirty’ water is sucked in, but more to do with being uniform with the circular flow direction you are creating in the tank. Being positioned here, the intakes complete the circle, by sucking in water at the last point of the circle, rather than intercepting water mid point in the circular path you have set it on, as it would do if the intakes were at the opposite side. That’s how I rationalise it anyhow.


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## Ivan Stoyanov (19 Feb 2021)

Hi, i have a little question, if someone can help me ofc. If I use 2 canister,  but have only co2 reactor attached to one of the canister. Which away can be co2 good distributed with spray bar along the whole back side of aquarium.  Thanks, if someone fixed this.


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## aquascape1987 (19 Feb 2021)

nigel bentley said:


> I will move the spray bars


As Clive points out, your hardscape arrangement will also affect flow, but I think this is a good place to start with tinkering to improve on the flow issue 😁


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## aquascape1987 (19 Feb 2021)

Hi Ivan,
I also use 2 x canister filters with 2x spray bars, but I have a CO2 feed to both of the lines.
Not sure if it is ok to have the CO2 on only one, but the reason I chose to do it this way,was because I wanted even the CO2 to enter the tank evenly at each side, and also didn’t want a mis match in flow output on each side from the two filters. Inline CO2 diffusers and reactors restrict the output of a filter. I figured that having an inline on one but not the other would create asymmetrical output from the filters.

I use a manifold to allow 2 x CO2 feeds from one bottle and regulator like this:


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## Ivan Stoyanov (19 Feb 2021)

I understand that with two reactors must be fine, but because I have one and will be little hard to split co2 on my regulator. I'm using 2 standard eheim Lili pipes pointed in same direction one from right back side with flow to left and other on back left side with flow to the front side. I have and one pump on front left pointing on to the right. Not sure if it's good, but I think it must be good with only one reactor.


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## aquascape1987 (19 Feb 2021)

Ivan Stoyanov said:


> I'm using 2 standard eheim Lili pipes pointed in same direction one from right back side with flow to left and other on back left side with flow to the front side. I have and one pump on front left pointing on to the right.



Do you have a picture of your set up, for clarity? If you have one, it may be a little easier to understand, and someone may be able to help/advise. 😁


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## Ivan Stoyanov (19 Feb 2021)

Yup my English is not so good.


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## aquascape1987 (19 Feb 2021)

Sorry mate, It wasn’t your English at all. It’s more that my brain prefers pictures rather than words in order to understand sometimes 😂

What are you using? Spray bars or some other type of outlet?


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## Ivan Stoyanov (19 Feb 2021)

Standard eheim lily pipes


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## aquascape1987 (19 Feb 2021)

Sorry, I have just fully worked this out now. My brain is not in gear today 🙄.

The flow appears circular on your drawing, but I’m not so sure it will achieve this in real life using the Eheim outlets, and pointing in these directions.

As I’ve said above, I personally would still advise spraybars along the full length of back  wall, holes pointing to front of the tank. Very slight upward angle.

Even if your Co2 is only on one feed/one side. It will still distribute CO2 around the tank, even if not quite as efficiently as having CO2 on both filters. But still effectively!

The main reason I did it with two is because I am picky, but I’m sure it would have worked fine with one feed only.


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## EA James (19 Feb 2021)

aquascape1987 said:


> I’m not sure exactly what you mean here, but I think what you are saying is that your intake(s) are in the front bottom corners?


I've just taken a few pics to better explain it, always helps IMO.
So the twin outlet, one points down to blast the co2 downwards and then across the front of the glass, the other one is pointing towards the surface for agitation but still in the same direction. The flow then eventually goes around the back of the tank and meets up with the intake so that's my flow pattern! 

Kinda difficult to explain in text but i was trying to get at is my flow circles around the tank in that way. With a spray bar the pattern changes, It's hitting the front of the glass then going across the bottom and up the back. So say in my tank for example, with the intake being on the right, how would the water on the left of the tank go through the filter? I know it all gets mixed up in the tank but It's not a direct feed if you like. 
Does that make sense? 

Cheers


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## aquascape1987 (19 Feb 2021)

Ah I see mate. If that works for you and gets flowing water everywhere then, that’s all that matters really. I would still recommend trying the spray bar though if you get the chance, as you were thinking of it anyway. You could give it a go for next to nothing cost wise.

I get what you mean about using a spray bar and the outlet being on one side only when using one filter.  Not sure how much of an issue that would present in terms of there being nothing at the other side to pick up that side of the final phase of returning flow. As you say, the water all gets mixed up anyway, so I would hazard it’s not that much of an issue, but I’m not an expert. Maybe someone else can answer this a bit more scientifically than me in terms of the physics.

But, thats why I chose to use two filters instead of 1, to make sure that I didn’t have an issue in this respect. It’s more about the symmetry of my system, rather than needing the extra filter flow, because  let’s be honest my tank doesn’t need the amount of filter power I’m using. Going by the rated flow of these filters, it is turning over 20x an hour, although in reality it will be less than this I realise.
Still, I figured the extra turnover  couldn’t hurt, as long as I could control it and it didn’t destroy everything and upset the fish (which I have managed to).

It’s each to their own methods on this, like many other aspects. This is just how I have found success that’s all. I by no means think it is the only way to create good flow however.


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## ceg4048 (20 Feb 2021)

Ivan Stoyanov said:


> View attachment 163204


Sorry Ivan, but as mentioned, this will never happen in real life. Water will never cooperate in the way you imagine. Spraybar on the back wall with holes pointing forward. This is THE starting point.

Cheers,


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## Easternlethal (20 Feb 2021)

I'm going to suggest something highly controversial. 

If you are using a diffuser and want to know the effects of flow on co2 distribution, turn off the pump or have it at the lowest level you can for a few hours then put multiple drop checkers all over the tank and see what happens to them.

The results might surprise you - because bad flow i.e turbulence excessive / surface agitation can actually decrease co2 in the water.

Having an understanding of co2 distribution in a tank before without flow makes it easier to calibrate it. Sometimes, a well placed powerhead is more effective than upping turnover - as far as co2 is concerned.


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## aquascape1987 (20 Feb 2021)

Easternlethal said:


> The results might surprise you - because bad flow i.e turbulence excessive / surface agitation can actually decrease co2 in the water.



I think it’s a given that surface agitation causes CO2 to off-gas and leave the water, but is necessary to oxygenate the tank.

So yes, CO2 is wasted by leaving the tank before being used by the plants for sure, but this is why it is fed in at a steady rate to ensure that there is a constant supply available around the plants and to them.
The aim isn’t to be efficient with CO2, but to make CO2 constantly available to the plants throughout the photo period irrespective of how much is wasted... CO2 is cheap, so wastage is not a concern.



Easternlethal said:


> If you are using a diffuser and want to know the effects of flow on co2 distribution, turn off the pump or have it at the lowest level you can for a few hours then put multiple drop checkers all over the tank and see what happens to them.


I think that CO2 would eventually saturate the water like this through the process of diffusion, but I’m not sure how relevant these results would be to the principles of Co2 distribution in a planted tank. If you employed this technique long term, your tank would not be a healthy one, and your plants would not thrive.


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## Easternlethal (20 Feb 2021)

My tanks will not thrive? Wow what a thing to say. Now I remember why I stopped posting here...

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## aquascape1987 (20 Feb 2021)

Easternlethal said:


> Now I remember why I stopped posting here...



Think you are perhaps taking something personal that isn’t personal. I haven’t said anything about your tanks... I’ve never seen them for a start 😂.

I just think that that what you are suggesting in terms of reducing flow as much as possible being a good move, is contrary to what my experience tells me is a good move. Each to their own, and absolutely no reason to get upset about it.


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## EA James (20 Feb 2021)

Easternlethal said:


> Now I remember why I stopped posting here...


UKAPS is probably one of the best forums going so I'm quite confused as to why you would say that?! 
I agree with @aquascape1987, You've taken that a bit too personally. Everyone is entitled to an opinion 

Cheers


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## Easternlethal (21 Feb 2021)

If the post had said "I don't think turning off flow would help because too much co2 would accumulate" then I would have gladly clarified that we're discussing how to calibrate flow so my proposal was to turn it off for a FEW hours to understand the co2 dispersion pattern within the tank before calibration. I would also have said that under those circumstances co2 accumulation depends on the rate it is being injected and depends on the geometry and topology of the tank, and if all drop checkers placed within a tank goes yellow within a few hours under no flow (which, by the way, I have never seen in a planted tank) then it means there is no issue with co2 dispersion and when you switch on the pumps a re-testand co2 dispersion decreases then you know that turbulence and degassing (due to increased surface agitation if your are using canisters) are the most likely causes for co2 loss - inside that particular tank and then you can calibrate your flow accordingly.

But he ended by saying this proposal was irrelevant and my tanks will not succeed that way etc. which is just a judgement and disincentives people like me from having any meaningful discussion. 

And on top of now I have to deal with being told that I am not tolerating opinion and am somehow attacking UKAPS, which just tells me that maybe I should be spending my time elsewhere.

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## ceg4048 (21 Feb 2021)

Easternlethal, I really don't think your ire is warranted here. Your post was possibly misunderstood, perhaps, as you say, there was confusion regarding turning pumps off permanently vs temporarily.

I for one, agree wholeheartedly with these sentences in your post:


Easternlethal said:


> The results might surprise you - because bad flow i.e turbulence excessive / surface agitation can actually decrease co2 in the water.
> 
> Having an understanding of co2 distribution in a tank before without flow makes it easier to calibrate it. Sometimes, a well placed powerhead is more effective than upping turnover - as far as co2 is concerned.


I cannot speak for aquascape1987 but I suspect he would agree also that of course, excessive turbulence and agitation off-gases the CO2. And yes powerhead=flow, so there is no debate there, however, the choice is as much for aesthetics as it is for effectiveness.

Now, I'll point out that you yourself opened your post with:


Easternlethal said:


> I'm going to suggest something highly controversial.


So here we are with controversy. Why bash the forum with statements regarding posting here due to controversy?
You are free to post here, or wherever you choose to, and while we wouldn't wish you to stop posting here, neither are we to be held hostage to someone's oversensitivity. Where is it written that meaningful discussion must be devoid of controversy?

I've not tried your test method with pumps switched off and multiple DCs mounted in various locations within the tank but it sounds fascinating. Can you elaborate further? Can you share any sketches or photos/videos? This might help others.

Cheers,


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## aquascape1987 (21 Feb 2021)

@Easternlethal - Polite gloves off now, because I’m not going round in circles with you, so this is my last reply to your ridiculous outburst here.

I’m on here to learn and talk about aquariums, not argue with people who get upset and offended as easily and unreasonably as a 5 year old school girl.

For the record:

I didn’t say *WAS irrelevant*, I actually said *NOT SURE** HOW* relevant....

In a normal mature discussion, that would simply be your cue to chime in and explain to me the relevance and perhaps correct me if I had misinterpreted what you were suggesting...... Look at the quote below- End of conversation on that one.



aquascape1987 said:


> I’m not sure how




On this aspect:


ceg4048 said:


> I cannot speak for aquascape1987 but I suspect he would agree also that of course, excessive turbulence and agitation off-gases the CO2


Yea, I’ve already said that:



aquascape1987 said:


> I think it’s a given that surface agitation causes CO2 to off-gas and leave the water


But I’m still unconvinced that turning the pumps off and mapping the RANDOM process of the molecular diffusion of CO2, will have any influence on practical application in my tank. E.g such as how high I turn up the flow valve on my filter, or if I change the position or direction of my spraybar. After this experiment, I personally, would still  be looking for as much evenly distributed flow around the tank as possible. I’ll just crank my bubble rate up to compensate for the CO2 losses through surface agitation, and my plants and fish will still be healthy.....

Perhaps though, in the spirit of healthy debate, if @Easternlethal had just put his argument across, as you do in an adult debate, and instead of being a little (a lot) over sensitive,there’s always a chance he might have convinced me otherwise. Like I said, I’m here to learn.




Easternlethal said:


> which just tells me that maybe I should be spending my time elsewhere



Im going to say something  controversial here as well... I agree with you.


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## nigel bentley (21 Feb 2021)

Back to my original post ref distribution of co2, I wonder what people's thoughts are on the velocity of water coming out of my spray bars. Flow seems to hit water surface halfway across the tank but I can see movement at front glass. Would this be sufficient or am I better off reducing length of spray bar thus increasing output. Bit of a conundrum for me 🤔
Also, sorry to open up a hornets nest with original post. 
As always, thanks for your help. 
Nigel


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## aquascape1987 (21 Feb 2021)

nigel bentley said:


> Flow seems to hit water surface halfway across the tank



I think that the spray bar would be better under the water.


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## nigel bentley (21 Feb 2021)

Sorry, I forgot to say, I'm just filling my tank after cleaning. The spray bars will be about 40mm below water surface.


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## aquascape1987 (21 Feb 2021)

Ok, so for me it’s hard to tell looking at the velocity of the water spraying out. I can only tell what’s right/wrong or too much/too little on my tanks  by filling up the tank as normal and watching things get pushed around the tank by the flow. Such as co2/o2 bubbles, fish food etc.


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## aquascape1987 (21 Feb 2021)

I have also messed around with the size of the holes in the spray bar as well to get the flow just right for me, without reducing the turnover of the filter. If you are going to do this though, you are better making some experimental spray bars using cheap tubing rather than your actual spray bars as you sometimes have to go too far with increasing the hole size before you find your ideal, and obviously the pipe is no good after that.
Then once I have decided on the size, apply to the actual spraybar. 😀


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## nigel bentley (21 Feb 2021)

Thinking the same, very difficult to establish from photo. Good tip reference observing food movement,thanks. Think I will keep spray bar as it is for now. I'm fortunate that the spray bars have joins so I can experiment in the future. Key for me is plants are growing quite well. It was just annoying me I had that blind spot. I guess I could also put plants in that position that tolerate a little less co2. Maybe some tall Crypts. 
Thanks again, it's always good to get another person's thoughts 🙏


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## Easternlethal (21 Feb 2021)

I was putting my argument across - maybe a bit too abruptly and directly, but they were factual observations - including about my own perceptions and I do not think I was making any personal attacks. 

@aquascape1987 @EA James - I do not think you understood my posts at all but sorry for overreacting. I was too blunt. 

@nigel bentley - You have identified a deficient spot in your tank and trying to figure out how to calibrate it. 

My point is that in order to know how much to calibrate your flow you need to get an accurate understanding of how it is affecting that spot, so you need another point of reference otherwise you would just be guessing how much to adjust. 

And the surest way is to turn off the flow and measure several points in your tank again (see diagram) because a) if one drop checker is yellow then you'll know your configuration is actually hurting that. If b) it stays the same colour then you'll know that your flow is not doing anything. If it goes blue then you'll know your flow has a slight effect over there. This baseline narrows down the possible culprits. Then, to narrow it down even more you look at all the drop checkers again and see how they ALL compare relative to when flow is on. If a) they are all a shade yellower then it's probably something which is affecting your tank generally (like surface agitation). If b) they are inconsistent (e.g they are yellow near the co2 diffuser but blue everywhere else) then you can rule out surface agitation and concentrate just on flow.

Depending on whether you want to address surface agitation or flow you will either adjust the velocity of the output spray bar (hole sizes) or the height (how near the water line and angle). If everything is equal and its just that one spot then maybe consider just adding a powerhead or drilling a hole in the spraybar to spray down to that spot and not change the rest because it's already working well and having 'conflicting' flow would not pose as much of a problem at this stage.

Of course you could just go with brute force and up co2, but that's not always a good approach especially if you later want to migrate towards a larger tank or a wet dry sump. I know that co2 is cheap but it's not fun having to replenish co2 canisters all the time.

Also you do not need to use having no flow as a point of reference. You can still compare two different flow configurations and develop a fairly robust hypothesis.

@ceg4048 here's your diagram. There's a lot to unpack and unfortunately I don't have a more elegant way to explain it and there's probably better ways. 

As background I have always used multiple drop checkers but I just refined it a little more after speaking to ADA design because when they developed their lily pipe some of us were a bit confused over how poorly it contributed to good flow (with most of the energy dispersed as soon as the water leaves the output). And I know that ADA designs entire systems so even though it's largely aesthetic, they would still have to be confident that their output stage could distribute sufficient co2 through their heavily planted Nature systems. The answer I got was that flow and diffusion worked together but can disrupt each other and they wanted to find that balance. In my LFS (most of them) I still find mostly heavily planted tanks maintained with less flow - sometimes just a tiny HOB and diffuser. So this method is my way to measure it as best I can using home equipment.



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## aquascape1987 (22 Feb 2021)

Ok so now we are getting somewhere to discuss it. It is an interesting concept, but what I do not understand about the method is:

If you switch off all flow whether it be power heads or filters, and eventually the water becomes perfectly still, and you then diffuse CO2 into the water, why would any particular spot not eventually become saturated with CO2 through the process of diffusion, given enough time and enough CO2?

My understanding of the physics of diffusion is that all areas WOULD become diffused with CO2 evenly under these conditions, eventually. My logic is that the CO2 molecules would enter the water, and randomly collide with, and be randomly collided with by the water molecules, and disperse in a random fashion in this way until they were eventually evenly distributed. So the question is, what would prevent a particular area of that body of water, from allowing CO2 to enter it in a perfectly still aquarium... And if the answer is that there is nothing that could prevent CO2 diffusing into a particular area of a perfectly still body of water, then what information does the experiment in fact show you?

I can perhaps understand this experiment if carried out by reducing flow/ surface agitation, but I’m not sure about stopping it altogether because of the logic above.

But again, I’m here to learn, and am open to learn as my logic on the physics is from high school level physics only. Perhaps there is something I am missing about how I understand diffusion?


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## Easternlethal (22 Feb 2021)

That depends on how high is the rate of co2 you're pushing into the tank. At a certain rate it would rather escape into the air than diffuse through the water column. It's only above that rate when it will start to accumulate. 

But the more co2 there is in the water the more eager it will be to escape so the rate at which you have to keep pushing co2 through is exponential and you will actually need a huge amount and a ridiculously large diffuser (relative to the tank size) to really get a still tank completely yellow. If you have a glass vase or nano tank, try it. It's not that easy. In any case wouldn't you still find it useful to know exactly how much co2 you need to push into your tank to make everything yellow? 

Of course if you already know then you already have a reference point and don't need to do the experiment. 

Also we're not talking about running the experiment the whole day. Just a few hours (just to see how quickly it gets there).

But that's actually another experiment for another time and for this experiment it actually doesn't matter. Because what you're doing is comparing it against WHEN you have flow and it's those DIFFERENCES in colour that you're interested in.


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## Easternlethal (2 May 2021)

Here is a 126 gallon extremely low flow low maintenance no fert high light co2 injected tank with 8 drop checkers. You can see from the picture that the surface is absolutely still but plants are pearling and growing well. On the top right you can see the front drop checker greener than the one behind which is rock solid blue - even though it is in the direct path of the inlet which sprays from left to right along the back. 

The outlet is near the inlet at the top back left hand corner of the tank.

The area with least flow is bottom front left hand side but drop checker there is also greener than the drop checker in the path of the inlet at the top, and has the heaviest amount of growth. There, I believe that Co2 is delivered through diffusion rather than flow.






DC barely visible but same colour as the crypt (dark blue green)




Pearling





Pothos suspended in the water column showing desired deficiencies from lack of nutrients in the water column (which keeps the discus happy)


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