# Measuring CO2 in low-tech?



## bugs (14 Oct 2009)

Anyone here measure their CO2 in low-tech non CO2 fertilised tank? If so, do you use a normal kit or some other method? Is it even measurable?


----------



## aaronnorth (14 Oct 2009)

It isnt measurable with a drop checker, the levels are that low it just shows as blue on a dropo checker.

pH/ KH charts dont work

the only viable way is to use a CO2 analyser if you have the cash!


----------



## bugs (14 Oct 2009)

As suspected... Thank you.


----------



## bugs (16 Oct 2009)

Hmmm... I got a reading. The drop-checker is green...


----------



## aaronnorth (16 Oct 2009)

either 
a) there is 25-30ppm of CO2

or 

b) it is a false reading, through innacurate 4dkh.

Im saying b as it is impossible for there to be that much CO2 in the water without injecting any!


----------



## bugs (16 Oct 2009)

aaronnorth said:
			
		

> ...through innacurate 4dkh.



Is this the "solution" that some buy to fill their drop-checkers? Mine is filled with tank water - as per the instructions. Perhaps that's my problem - following the instructions


----------



## CeeJay (16 Oct 2009)

Hi bugs.
Using tank water is your problem for sure.
My JBL instructions said I should use tank water too   but I quickly learnt that this is worse than useless.
4dkh is the way to go   .

Chris


----------



## John Starkey (17 Oct 2009)

Hi the best way is to look at your plants,if it's low tech then you don't want high levels of co2,
if plant growth is good then you don't have a problem,if you are having a problem then try easy carbo,if you already doing so and you are not having good ant growth then you could run co2 at a rate of say 2/3bps,bit my main thinking is why would you want to measure co2in low tech tank anyway?
Regards john.


----------



## bugs (17 Oct 2009)

I had a CO2 kit from when I did high-tech etc so thought I would just see what is told me. I realise measuring CO2 in a high-tech is more about avoiding overdose but was just curious to see what was happening.

I have got some plants that are not doing as well as others but it's still early days so I just need to experiment a little to see what's not right for them.


----------



## ceg4048 (17 Oct 2009)

bugs said:
			
		

> I had a CO2 kit from when I did high-tech etc so thought I would just see what is told me. I realise measuring CO2 in a high-tech is more about avoiding overdose but was just curious to see what was happening.


This statement isn't true at all. It's easy to tell if you have overdosed CO2. just look at the fish. They'll tell you right away. You don't need a dropchecker for that. Using a dropchecker is all about making sure that you are within the range of what is enough CO2, but again, as J. Starkey mentioned, the measurement is used to corroborate your observations. If there is a conflict between what you observe and what the dropchecker says then that means the dropchecker is wrong.

If you are not injecting CO2 then the dropchecker won't tell you anything. It's just a pH test kit, that's all. So if you see a green dropcheker reading on a non-injected tank all that means is that whatever water you put in the dropchecker has a neutral to slightly acidic pH. But if you are putting tank water in the dropchecker why do you even need the dropchecker? Just measure the tank water pH directly and your pH test kit will tell you exactly the same thing - that your tank water has neutral to slightly acidic pH. No mystery there, but you still have no idea what the level of CO2 is.

For a non injected tank one can safely assume that the the CO2 concentration near the top of the tank is somewhere on the order of 8-10ppm. Again, no mystery here because that's simply the bog standard equilibrium concentration between water and atmosphere. If you put 4dkh water + reagent in the dropchecker, you should expect, after a while, that the solution will turn dark green or green/blueish indicating a pH of somewhere between 7 -7.2.

Cheers,


----------



## bugs (17 Oct 2009)

Lucky I'm not the sensitive sort... It was an opinion - perhaps I should have been more literal. The point I was making around questioning the validity of using a drop-checker for a low-tech versus a high-tech was perhaps too subtle. 

Assume for one moment that you can measure the concentration of CO2 in both a high-tech and low-tech. It follows then, that the person testing would be...



> ...making sure that you are within the range of what is enough CO2,



Whilst obviously...



> the measurement is used to corroborate your observations.



So, when challenging why someone would want to test a low-tech whilst accepting that it perfectly normal to test high-tech is it not reasonable to cite that one key difference is you can overdose on a high-tech, thus making testing on a high-tech significantly more meaningful in this respect?


----------



## ceg4048 (18 Oct 2009)

bugs said:
			
		

> Lucky I'm not the sensitive sort... It was an opinion - perhaps I should have been more literal. The point I was making around questioning the validity of using a drop-checker for a low-tech versus a high-tech was perhaps too subtle.


Yes I agree. It's always better to be literal in scientific discussions. Subtlety is often the servant of confusion.



			
				bugs said:
			
		

> Assume for one moment that you can measure the concentration of CO2 in both a high-tech and low-tech. It follows then, that the person testing would be...
> 
> 
> 
> ...


But this is not the key difference. Let me explain to you the key difference:

In a high tech tank you can change the CO2 concentration from minimum ambient levels to outrageously high levels. It's entirely conceivable that you can drive the CO2 concentration to levels that will obliterate fish and so it's entirely feasible to have a high tech tank intentionally devoid of critters. In fact, I often suggest this method to would-be high techers when starting up a tank. The dropchecker can still be useful in determining levels regardless of whether you have critters in the tank or not. When using the dropchecker in high tech, an often used technique is to drive the injection rate as high as possible while observing the comfort level of the fish. In one tank it's possible to have a green dropchecker and uncomfortable fish while in another tank it's possible to have a yellow dropchecker with fish that are comfortable. It therefore depends on the fish as well as the other parameters of the tank. Therefore a dropchecker does not reliably tell you whether you have overdosed, but it can sometimes confirm that you have done so. In a high tech tank therefore, overdosing critters is addressed by using small adjustments to the injection rate while observing the fish. It's definitely not done by looking at the dropchecker because you can vaporize your fish long before the dropchecker will tell you anything. 3 hours later, it will then confirm that you fish ought to have been wiped out. Have a read of the dropchecker article in the Tutorial section, where these and other subtleties are discussed.

By definition, in a low tech tank, one typically cannot appreciably affect the CO2 levels. That's specifically why it's pointless attempting to measure it because the levels will be a direct function of the ambient conditions and is usually a standard value depending on altitude and other local environmental conditions. Now, for academic reasons, if you wanted to determine, with as much precision as possible what that value is inside the tank, then yes, a dropchecker can be used to determine some basic values. In this case 4dkh water does not provide sufficient resolution, i.e. a small pH change results in relatively large ppm change. Using 1 dkh or even a 0.5 dkh water inside the checker will provide better accuracy at these lower CO2 concentration levels.

Hope this makes sense.   

Cheers,


----------



## bugs (24 Oct 2009)

This thread has got me thinking... One thing that irks me is being sold a CO2 testing kit that will not accurately measure CO2 without an additional purchase. It's not even clear that an additional purchase of 4dk solution is prudent when the instructions clearly state that tank water should be put in the drop-checker.

This is an area where I suspect UKAPS as a body could lobby suppliers of aquatic kit to get their act together. Or am I being too harsh?


----------

