CO2 in situ meter measurements, real time data on localized CO2 ppm readings

VaughnH

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Nutrients, including CO2, are in the water to be consumed by the plants. As the plants consume them, they are no longer in the water. Areas of the tank where plants are consuming the nutrients rapidly will be starved for nutrients unless something moves more nutrients into that area to replenish those which were consumed. That is the role of water circulation. Diffusion of nutrients from high concentration areas to lower concentration areas isn't nearly as rapid as good water circulation is, and it depends on the gradient in concentration to make it occur, but we don't want gradients in nutrient concentration.

Neither you nor I have a good enough excuse to be lazy! That sucks.
 

yme

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very intesersting!
What would be the price of this product? probably quie expensive. but maybe a your local fish club can invest in such a device. I would be interested!

greets,

yme
 

Chiya

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Hoppy,

LOL.. Well, I was just hoping for that tiny bit of excuse.
Jokes aside, thanks for your explanation.

I always thought that the diffusion happens very fast (think about a drop of colored water in a pail of clear water)

So just a bit of circulation might boost that diffusion rate two-fold? ten-fold?

If we go low light, the uptake of nutrients is slower, will diffusion be enough to 'spread' the nutrients around?

I'm having this idea in my head about achieving 1mph in our tanks.
A wave-maker perhaps?

Regards,
Ryan
 

VaughnH

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Chiya;28643 said:
Hoppy,

LOL.. Well, I was just hoping for that tiny bit of excuse.
Jokes aside, thanks for your explanation.

I always thought that the diffusion happens very fast (think about a drop of colored water in a pail of clear water)

So just a bit of circulation might boost that diffusion rate two-fold? ten-fold?

If we go low light, the uptake of nutrients is slower, will diffusion be enough to 'spread' the nutrients around?

I'm having this idea in my head about achieving 1mph in our tanks.
A wave-maker perhaps?

Regards,
Ryan

Calculating how fast diffusion happens is beyond the scope of this course. (One of my old college professors loved that comment!) Seriously, I have no good idea about how fast diffusion takes place, but I do know that when I add trace mix to my tank, the "cloud" of haze it causes doesn't disappear very fast.

Intuitively, you would have to conclude that low light tanks don't have nearly the problem with local nutrient depletion that high light tanks do. But, they also don't get the high nutrient concentrations that high light tanks get, so it could be that they need the circulation too. Tom's references on water circulation mentioned one mph as a water velocity that is good, but that is a very high current for a small tank. It is about 18 inches per second - about 2 seconds for all of the water on the left side to move to the right side! Since the flow in our tanks is very chaotic, it may be that eddies and other local water movement can be that high a velocity. In any case, it does give a feel for what good water movement really is.

Koralia type power heads, which use a "boat propeller" to move water, are very good for achieving the circulation we need - much better than ordinary power heads.
 

calihawker

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On my 300 gallon tank the current c02 distribution method is a diy reactor with a magdrive 9.5 and spray bars along the top pointing straight down into the plant bed. This is in addition to 2 xp3's an xp4 and various powerheads for a total of about 2500 gph distributed around the tank.

I have a plan to change it all over to a sump design with high flow, maybe wave makers etc. but after reading this thread I was wondering if the solution, in my case, is to put the spray bar down on the garvel pointing up. Is'nt it right down in the plant bed that Tom is measuring the least amount of c02? With the spray bar on top, I can't be getting any c02 at all down in the plant bed in my 30"deep tank.

Very easy to try before ripping all the plumbing out.

Steve
 

VaughnH

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It does seem that the water containing the incoming CO2 should start its journey around the tank at the bottom of the tank. Any bubbles of CO2 would then have the maximum of time to reach the most plants before finally rising to the top of the water. Right now my CO2 is by a mist method and the Koralia which blows it around is near the bottom of the tank.
 

Gerryd

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Tom,

Do you recommend the data logger option for this meter? I am going to order one in the next 2-3 weeks and wanted to know if you had it and if it is worth the cost.....

Did you actually buy it from WMT? I am a little concerned about spending that much $ over the web from a company I never did business with before......

Thanks,
 

yme

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I also bought the same co2 analyser without datalogger. just to expensive :D

I don't miss it either.

As for the measurements: for me it really takes a long time to give a stable readout >30 minutes. But I do measure everywhere more or less the same CO2 levels : 30-35 ppm. I do not see a gradient. Nor is it much lower in the plants.

btw: what are the calibration fluids? I got a little flask of it but that is now finished and it is almost time to recalibrate: tom, do you know??

yme
 

Gerryd

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Hi yme,

Good to know about the logger.............

When you say 'stable' for 30 min is that because the meter won't stay at a certain reading and fluctuates?

The specs say the response time is about 5 minutes, and if the tank c02 level is NOT equal in the tank, as Tom thinks, then I would expect it to vary it's readings, even in the same spots..

From their site:

Accuracy: Depends on calibration. Practical accuracy up to ± 1 mg/l.
Response Time: Typically 5 minutes at 20°C depending on flow velocity past probe. In stilkl water, up to 15 minutes.
Flow Requirements: The instrument does not use carbon dioxide for its measurement, but a certain flow is necessary to ensure that the sensing element of the probe is in equilibrium with the surrounding water, and to avoid "spot" measurements.


On the WMT website on page 1 of this thread, they mention 100ml calibration fluid as part#

G02XCS 100ml Calibration solution.

So you can just order that if needed...........

BTW, did you buy yours new and from WMT or from where? I have not seen these on e-bay :)

Are you glad you got it and was it worth the $ to you?

Appreciate the reply...........
 

yme

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hi gerryd,

of course you can buy the stuff, but since I work at a lab, possibly we have it on the shelf :D

What I meant is that the Co2 levels keep increasing for about 30 minutes. first fast (the first 5-10 minutes) and then more slowly. untill it levels off.

I ggot mine from the dutch distributor, catvis bv.

Is it worth the money: yes and no. You get accurate readings, but since my co2 levels were the first time I measured around 60 mg/l I did not have a co2 shortage. i did explain though why my shrimps died :(
And I must say that the pH-KH tabel is pretty applicable for my tank. maybe 5 mg/l off, but still, very decent.
And do I now have a great tank?? No.... plant growth is still poor and not very healthy. pogestemon still stunts etcetc. In that respect the very expensive thing is not the holy grail towards a vibrant algae free tank.

On the other hand: I am still glad that I bought the thing, I would buy it again.

greets,

yme
 

Gerryd

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Hi yme,

but since I work at a lab, possibly we have it on the shelf

Well that's not fair lol

I don't expect it to be a holy grail at all. I have excellent growth and little algae now, but would love to actually confirm what the c02 levels are with my setup and how it changes as the mazzei and bypass valves are adjusted......

Does more misting result in higher/quicker readings?

It was great knowing my PAR values, although that meter was a lot cheaper lol

A lot to pay to satisfy my curiosity I know, but I will hook this up 24/7 (can I do this?) if possible so at a glance I will see what is up.......

Glad to know you would buy it again.........

I had stellata and grew like a weed....... something is off if it is not growing........I very rarely have a plant that will not grow well once it settles into the tank...stellata, inclinata cuba, etc.

What are your specs, dosing, lights, etc?

Appreciate your time.
 

Tom Barr

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yme;34447 said:
I also bought the same co2 analyser without datalogger. just to expensive :D

I don't miss it either.

As for the measurements: for me it really takes a long time to give a stable readout >30 minutes. But I do measure everywhere more or less the same CO2 levels : 30-35 ppm. I do not see a gradient. Nor is it much lower in the plants.

btw: what are the calibration fluids? I got a little flask of it but that is now finished and it is almost time to recalibrate: tom, do you know??

yme

They should have calibrated it at the factory. I check it with the stirring chamber about once every 6 months or if I want to be careful and recheck things.

The long stabilization times are worrisome, I'd calibrate it.
5 min is plenty of time for most cases, you should calibrate.

You might try 40-45ppm range of CO2 and note the difference(assuming the 30-35ppm is good). Even at moderate lighting, I found this to be good, but much more than this, fish may suffer. This is for Discus, they tend to be much more sensntive to high CO2 than other fish and these are very large discus.

They are good for this due to larger size(larger fish are more sensitive-high O2 demand) and discus have a nice dark color change when stessed.

I'm a bit leary suggesting 40-45ppm to folks because their measurement and monitoring is often poor and the risk is high. However, with this meter, if it's calibrated, you should be able to safely add CO2.

They see what the real CO2 ppms are that infleunce fish etc.

A trick you can do to get instenaneous CO2 is to withdraw a sample of water in the region of interest in the aquarim. Then place it in a sealed chamber with the CO2 meter probe sealed in side. As long as the trasnfer prcoess and chamber are sealed and no CO2 is allowed to degas, then you can take all the time you want to get to CO2 reading.

Then you know what the CO2 when you withdrew the water at that location.

I think a flow through sampling chamber you can pull water through into the chamber is ideal for this.

See here:
http://www.rickly.com/wqi/images/FLOWCELL.JPG

http://www.ottoenvironmental.com/products/50216.jpg

And simply add a gas proof seal for the CO2 probe.

Regards,
Tom Barr
 

bibbels

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How much do these meters cost? I have been considering the puchase of one this year.
 

Gerryd

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Hi,

I think over $2000 US..............

I am requesting a quote in the next week or so and will let you know.......
 

yme

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hi!

I did the recalibration: my osmsis water was 002, ading the calibration fluid gave 000, A gave: 009, B gave: 56, U= 9.57, K=59.57

I had to adjust the slope a bit. I measured again, and again the response time was very slow in the tank. This was not the case during the calibration, so I decided to measure the CO2 levels of my tank in the calibration column (and used parafilm to seal the top). This gave a reading of 38 ppm quite fast. anyway, I lowered in the tank the pH by 0.1, measured in the column and got a CO2 level of 55 ppm. a bit to much.... so now I increased again the ph by 0.05.

anyway, it seems that the flow is quite important for a fast measurement. eventhough I have quite nice flow in the tank (which can be nicely visualised by the co2 microbubbles), but not enough for a fast measurement. And I guess that my co2 sensor is oke and not damaged ....

and about my tank: I don't think this is the right tpoic to discuss it: I will continue my "old" thread: "optimizing everything...."

greets,

yme
 

Tom Barr

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Hi,

YME this is not off topic here.
The flow issue is true for pH, O2, and CO2.
I place the probe in the higher flow regions, these also tend to be where the higher CO2 readings are for me and for likely most aquariums.

But yes, certainly flow rates by the sensor will affect response time.

Stick with 35-40ppm range.

Regards,
Tom Barr
 

Tom Barr

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Sure, but place a measuring tape on the tank glass, add CO2 mist and follow and time the bubbles, that will give you the rate of flow..............

Just be good at timing.

Reards,
Tom Barr
 

Gerryd

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Tom and yme,



I got the prices from the vendor and want to confirm what exactly I want to get.

Vendor e-mail is as follows:

G02: OxyGuard CO2 Analyzer

G02C2 $1,755.35 OxyGuard CO2 Dissolved CO2 Analyzer - probe and transmitter with 7 metres of cable. For 230 VAC, other voltage on request.
G02C2P $2,556.27 OxyGuard CO2 Dissolved CO2 Analyzer - Portable Version with rechargeable batteries. With probe with 3 metres of cable, calibration accessories as per item G02C2CAL and charger for 230 VAC, other voltage on request.
G02C2PLOG $3,246.27 OxyGuard CO2 Dissolved CO2 Analyzer - Portable Version with rechargeable batteries and Data Logger. With probe with 3 metres of cable, calibration accessories as per item G02C2CAL and charger for 230 VAC, other voltage on request.
G02C2CAL $351.69 Calibration accessories: Beaker with stirrer and magnet, 75 g pH conditioner, dosing spoon, 100 ml calibration solution, dosing syringe, adjustment screwdriver. These calibration accessories can be used for more than one OxyGuard CO2 analyzer.
G02XCS $50.28 100 ml calibration solution.
G02XCT $16.90 75 g pH conditioner.
G02STB $75.85 12VDC Battery Pack.
G02STC $52.18 Charger for Battery Pack for 230VAC mains.
$-
G02XBOXB $292.89 Travel Box for Portable OxyGuard CO2 Analyzer and accessories. Colour: Black.
G02XBOXO $292.89 Travel Box for Portable OxyGuard CO2 Analyzer and accessories. Colour: Orange.

I THINK I want the G02C2P in bold above. Not sure about the bold/italics G02STB.

Also I do not think I want 230 VAC or am I wrong? I am confirming with the vendor but would appreciate your thougts. I don't want to spend for something I do not need...........

Thanks again,
 

yme

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hi!

I have the pc CO2 meter Oxyguard, portable model (G02C2P).

in europe we have 230 volts so I have the 230 VAC variant.

you probably need the 115 volts version.

grrets,

yme