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Estimating CO2 injection rates in ml per minute

ShawnMac

Member
Joined
4 Aug 2015
Messages
123
Location
ND, USA
I'd like to request that members take a little time to estimate and post their CO2 injection rates in ml per minute. Many times we try to compare CO2 levels or injection rates using bubbles per second, which as many experienced hobbyists know, isn't that helpful. The bubbles are on different equipment and under varying operating pressures, which all impact the size of the bubbles. If we are able to start gathering some information on injection rates in ml per minute, diffusion methods, tank size, light levels, and plant mass; we might better be able to compare methods and help beginners find an injection rate with which to start based upon their specs.

Of course this isn't a replacement for good horticulture like observing plant growth and other methods to estimate CO2 concentration (drop checker or ph/kh chart), but it could be another tool to help people get it right or trouble shoot problems.

To estimate your injection rate use a graduated cylinder inverted over your diffuser, so that it captures the bubbles. Make sure the cylinder is full of water so that the CO2 can displace the water. In my case I had to use a small graduated cylinder and a small plastic funnel (all from my DIY ferts kit) to capture the bubbles and funnel them into the cylinder. After 60 seconds I measured 1.4 ml of CO2 gas trapped within the cylinder. It is best to do it this way for diffusers and atomizers since they are under some working pressure which effects the gas volume while still in the line or bubble counter. Removing the diffuser and putting the line straight in could change the injection rate to be measured.

The method will have to be adapted for other injection methods like reactors by simply taking the line off the reactor and running into the measuring cylinder. While these systems are under some working pressure, it is much less than an atomizer...so hopefully there won't be a significant change to the bubble rate.

I'll start:

45 cm aquascape with medium plant density (Iwagumi-ish) and high light. Moderate surface agitation, no skimming

Injection rate 1.4 ml/min through ADA pollen glass diffuser.


Also, if you have any comments on the method please share them. I should add that this is not my idea, this was proposed by Tom Barr some years ago, however the method has never caught on. I hope we can change that.
 
How hard i try, what goes beyong my understanding what one would like to adchieve with this knowledge.. But besides that, I noticed in my case getting a very stable bubble count was near impossible. With a stop watch and my bad eye/hand coordination added. This probably is caused by the reducer/needle valve quality and age versus inveronmental temperatur or what ever other influence. I made the choice to invest in a ph controler istead of investing in a new reducer with the chance ending up with the same issue. At least with a ph controler i know a fluctuating bubble count aint such a big deal anymore.

I gues if you measure per minute one needs to be very sure that the bubble count is perfectly stable if not the estimate could be very far off at the end of the day with +/- the 600 minutes co2 is aded over the day.

But if i would like to know the ml/minute estimate i think monitoring the weightt of the botlle over a longer periode you could calculate back the average co2 use per minute a bit more precise.

What you need to know is the co2 volume/weight equivalents and los of weight from the bottle over x hours. Then it all comes down to the size of the bottle and quality of the weight scale you would use. Having a small co2 cardridge or a 500ml bottle a kitchen weightscale would do the job perfectly. :)

I would like to assist you with your experiment, but since i use a 5 kilo FE i do not have the scale to pull it off. So i only can launch an idea how to get the estimate a bit more precise without fiddling around in your tank water. Maybe someone with a small soda stream cardridge gets curious and like to give it a go.. :thumbup:
 
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Much better is gr of CO2 per hour per litre as much easier to measure, is completely independent of injection method and can be done without disrupting your carefully configured CO2 setup.

I use a set of Argos digital kitchen scales to weigh my FE at start of CO2 on time and at end of the day. I am using 15gr of CO2 in 8hours in 180litres with a green to yellow drop checker.

That works out 15/180/8 about 0.01gr per hour per litre.
 
Much better is gr of CO2 per hour per litre as much easier to measure, is completely independent of injection method and can be done without disrupting your carefully configured CO2 setup.

I use a set of Argos digital kitchen scales to weigh my FE at start of CO2 on time and at end of the day. I am using 15gr of CO2 in 8hours in 180litres with a green to yellow drop checker.

That works out 15/180/8 about 0.01gr per hour per litre.

What if you have a leak? how do you measure the co2 actually getting to your tank?
 
What if you have a leak? how do you measure the co2 actually getting to your tank?

You shouldn't have one.. :) This is very easy to check, with a spray bottle filled with some water with dishwashing soap.. Spray it on every threaded connection and hosefitting. Even with the smallest leak you see little soap bubbles form.. This you should check everytime you even tough and move the bottle.. Just make sure you do not spray that stuff in your tank water and be carefull with the electrical part of the solenoid if you use one. Cover the solenoid with a dry cloth and only spray a tiny bit on the hose connector.
 
What if you have a leak? how do you measure the co2 actually getting to your tank?
If you have a leak, like I have had many times, then my consumption goes above 15gr a day. Easy peasy indication of a leak.
 
Its nice to hear other methods. I think we can all agree that bps is not useful.
 
I can. :)

Download an app to your phone called BPM. Then Tap away for every bubble you see for around 30 secs so a good mean BPM figure is established. Then simply devide by 60.

See image:

1b374b854844156dae8ad7850722ac8f.jpg

Here you can see I tapped away for 144 bubbles which gives a bpm of 257. I convert the bpm in bubbles per second by deviding by 60 so 4.28bps

Sounds more complicated than it is.
I then log that figure with the time of day and pH of the water to plot pH drop.

Handy to do weekly once dialled in and also when swapping cylinders.

Sent from my E5823 using Tapatalk
 
Yes. Just plonk cylinder + regulator on scales at each water change. Write on cylinder the date and weight so can track how long the cylinder has left. Weight is about 5.7Kg for a new cylinder, dropping to 3.7Kg obviously when empty.

I like this, Much how I used to do to determine weight of large cichlid's I occasionally care/cared for to see what food's produced the most weight gain.
I simply took plastic specimen container and filled it to near middle with water and weighed it.
Then insert the fish and weigh the specimen container again.
The difference was the weight of the fish.
Could track this over week's.
 
Who can honestly say they can tell the difference between 4 and 5 BPS? When i used a inline diffuser the BPS was uncountable.All it can give us is a ballpark figure really?

I use glycerine in the bubble counter which can slow the bubbles down a little.
 
I like this, Much how I used to do to determine weight of large cichlid's I occasionally care/cared for to see what food's produced the most weight gain.
I simply took plastic specimen container and filled it to near middle with water and weighed it.
Then insert the fish and weigh the specimen container again.
The difference was the weight of the fish.
Could track this over week's.

Hand's down, Hikari bio gold and chopped earthworm's produced best for me.
 
Has anyone tried to keep the cylinder on a set of scales constantly....Would this be ok to do? Would it affect the accuracy of the scales?
 
I can. :)

Download an app to your phone called BPM. Then Tap away for every bubble you see for around 30 secs so a good mean BPM figure is established. Then simply devide by 60.

See image:

1b374b854844156dae8ad7850722ac8f.jpg

Here you can see I tapped away for 144 bubbles which gives a bpm of 257. I convert the bpm in bubbles per second by deviding by 60 so 4.28bps

Sounds more complicated than it is.
I then log that figure with the time of day and pH of the water to plot pH drop.

Handy to do weekly once dialled in and also when swapping cylinders.

Sent from my E5823 using Tapatalk
Even if you can, and I still doubt the accuracy of the taps. BPS is not useful because there is too much variation between systems. A more standardized method makes comparison better, although still not perfect.

The ph drop part is even more of a shot in the dark than the bubble tapping. Without knowing the kh value there is not an accurate way to estimate ph drop, it's just a wild guess.

sent from tapatalk on my phone so auto correct and other errors are bound to happen
 
Without knowing the kh value there is not an accurate way to estimate ph drop, it's just a wild guess
You don't need to know your kH, pH drop is independent of kH, which is why you measure a change rather than an absolute value. Thus a 1 point drop in pH is about 30ppm CO2 regardless of your waters kH.
 
KH acts as a buffer. The higher KH the more CO2 required to move the ph. It buffers the effect.

sent from tapatalk on my phone so auto correct and other errors are bound to happen
 
KH acts as a buffer. The higher KH the more CO2 required to move the ph. It buffers the effect.
n
I think Ian means for the pH ranges that's common for aquariums, a 1 unit drop in pH roughly indicates about 30ppm of CO2 is around.
 
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