Estimating CO2 levels - The Planted Tank Forum
 68Likes
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 40 (permalink) Old 04-16-2020, 08:40 PM Thread Starter
Algae Grower
 
PTrader: (0/0%)
Join Date: Jan 2018
Location: Upstate NY
Posts: 64
Estimating CO2 levels

Hope this is the right forum for this question. I know has been thrashed ad nauseum over the years but I have another perspective I'd like feedback on which may simplify guesstimating CO2 in the water.


It seems to be understood that drop checkers and pH are very rough guides to knowing if you are injecting enough or too much CO2, and watching for fish to gasp at the surface is the least desirable metric. pH is considered flawed due to all the other variables which could be affecting it. But why not instead of using an absolute pH value, use a value difference from what you know your natural pH to be. My tanks run at around 8 for a natural pH. After 15 months not much I did (save trying peat) changed it. Starting CO2 injection (and using a Milwaukee SMS122 pH controller) I found I could lower it and I have, to 6.9-7.1. Stop the CO2 for a day and it returns to 8. So if nothing else changes, couldn't I use that delta as a more accurate estimation of how much CO2 is actually in the water column?
ChuckM is offline  
Sponsored Links
Advertisement
 
post #2 of 40 (permalink) Old 04-16-2020, 09:00 PM
Planted Tank Obsessed
 
pauld738's Avatar
 
PTrader: (0/0%)
Join Date: Jan 2019
Location: Modesto
Posts: 315
I think it's always been that difference, rather than an absolute value. Although I too see alot folks focus too much on an absolute pH value. I know I only look at the relative change to give me an idea of what's going on. Although using this method does rely on starting co2 concentration.

No guarantees that I didn't over simplify a complex topic

Sent from my Pixel 3 XL using Tapatalk
pauld738 is offline  
post #3 of 40 (permalink) Old 04-16-2020, 11:04 PM
Planted Tank Enthusiast
 
PTrader: (0/0%)
Join Date: Jan 2019
Posts: 633
Well, I'm pretty sure this is exactly the recommended advice. Check your starting and ending ph. There is also a plethora of ph, kh and co2 charts out there that do exactly this.
Ddrizzle is offline  
 
post #4 of 40 (permalink) Old 04-17-2020, 01:17 AM Thread Starter
Algae Grower
 
PTrader: (0/0%)
Join Date: Jan 2018
Location: Upstate NY
Posts: 64
Quote:
Originally Posted by Ddrizzle View Post
Well, I'm pretty sure this is exactly the recommended advice. Check your starting and ending ph. There is also a plethora of ph, kh and co2 charts out there that do exactly this.
I guess I missed the one(s) that use a delta. I am familiar with the one that says if your pH is x and your kh is y, your CO2 is z. And that's been roundly discredited because of what I cited above. There are other factors that could affect pH making it unreliable.
Am I missing something?
ChuckM is offline  
post #5 of 40 (permalink) Old 04-17-2020, 01:23 AM
Planted Tank Guru
 
PTrader: (0/0%)
Join Date: Jul 2018
Posts: 2,196
Quote:
Originally Posted by ChuckM View Post
...I am familiar with the one that says if your pH is x and your kh is y, your CO2 is z. And that's been roundly discredited because of what I cited above. There are other factors that could affect pH making it unreliable.
Am I missing something?
Yes, that's correct. There are too many variables affecting ph and kh that makes the chart useless many times. For example my current tank has a KH of 11 (thank to seiryu stone) and a PH of 6.5 (with co2) giving me a whopping 105ppm co2 according to the chart.

Pretty much the best we have is the double drop, ph and checker.
Quagulator and ChuckM like this.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

2 Foot Rimless Tank - Under Construction


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Asteroid is online now  
post #6 of 40 (permalink) Old 04-17-2020, 12:24 PM
Planted Tank Guru
 
Quagulator's Avatar
 
PTrader: (0/0%)
Join Date: May 2015
Location: Forest City ON, Canada
Posts: 2,309
Yea, most advice I am seeing / am giving out is the drop in pH from CO2, not the absolute pH value. It's the same as when I ask for what fertilizer they are dosing at what rate, and I'm told "Thrive 2 pumps a week".... that tells me virtually nothing... it's the same as someone stating a single pH value / kH, we need the two data points to determine the drop / CO2 "concentration".

Ideally you want at least a 1.0 (up to 1.4 ish on the higher end) but consistent drop of pH from CO2 enriched water vs degassed water for the entire photoperiod. I understand that is tough to achieve this from the second the lights turn on to the second they turn off without a pH controller, but try and get it close (an hour or two of "less than ideal" pH drop is usually fine). Obviously aiming for the entire photoperiod would be best, but it's not always achievable in everyone's equipment and financial setup.

I've been in countless arguments (not driven by me) on other forums regarding pH drop and that pH/kH/CO2 chart. Usually I get displayed as a "know it all with a straight line, single lane of thinking, blah blah blah" when all I'm doing is helping someone running a 75 gallon tank at 2 bubbles per second of CO2 really start to actually see the great benefits of CO2 if they would crank it up to a full 1.0 drop.

I'm ranting... (can you see my frustration from these arguments lol?)
Greggz, ChuckM, Ventchur and 1 others like this.

"No Ice? Just Freeze Some Water"
My Dirted 10 Gallon High Tech:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Quagulator is offline  
post #7 of 40 (permalink) Old 04-17-2020, 12:50 PM
Planted Tank Guru
 
PTrader: (0/0%)
Join Date: Jul 2018
Posts: 2,196
The drop has always worked for me. It worked in my tank with kh of 4 (out of tap) and it seems to be working in my tank with Seiryu stone and a kh of up to 11 before water change. I go for the same approx. 1.0 drop and a lime green checker. Fish aren't stressed and the plants seem good.

As far as dialing in what works, when to turn co2 on, etc that to me is definitely a feeling it out, since every tank is different. Perfect example I'm using a 24/7 cycle where there is some light on 18 hrs a day. I'm only running co2 10 hrs. Reason being I have very little surface agitation so my drop checker is only slightly darker green than where it is at peak. So there is good co2 already in the tank 24/7. Someone else with the same setup, but had more surface agitation, might need to run co2 longer.
Quagulator and ChuckM like this.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

2 Foot Rimless Tank - Under Construction


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Asteroid is online now  
post #8 of 40 (permalink) Old 04-17-2020, 02:39 PM Thread Starter
Algae Grower
 
PTrader: (0/0%)
Join Date: Jan 2018
Location: Upstate NY
Posts: 64
I think what I'm aiming for is to get an absolute value for the CO2. I can drop my pH down a full point or so on a schedule that starts just before sunrise and ends 2 hours before the lights actually go out, and except for a minor disaster a couple weeks ago with some new Reticulated Hillstream Loaches, everyone else has seemed content for going on 2 months now on CO2, and several years in my possession. And the plants look great (and did not before the CO2). But what I'd really like to know, and didn't convey very well, is an actual ppm value rather than an "oughtta be".

I see there's a $50 Hach kit that will measure CO2 which I *could* go for, but for how often would I use it it might be overkill.
Ultimately I want an adequate amount of CO2 dissolved in the water with a minimum of waste.

Thanks much for all the feedback.
ChuckM is offline  
post #9 of 40 (permalink) Old 04-17-2020, 02:51 PM
Planted Tank Guru
 
Quagulator's Avatar
 
PTrader: (0/0%)
Join Date: May 2015
Location: Forest City ON, Canada
Posts: 2,309
Quote:
Originally Posted by ChuckM View Post
Ultimately I want an adequate amount of CO2 dissolved in the water with a minimum of waste.

Thanks much for all the feedback.
Start at a 1.0 drop and fine tune it slightly higher to your tank's needs. That's the best we can do with hobby grade equipment.

I guess you could look into proper lab based testing but... expertise, finances and lab experience play as much of a role in the outcome as the actual test would.

A drop in pH of 1.0 roughly = 30-40ppm of dissolved CO2.

Want a numerical value? Buy a flow meter and measure the CO2 consumption in cubic centimeters per minute.

Want zero waste? Install a reactor that achieves 100% dissolution.

Want thriving plants? Accept some waste is needed to achieve a consistent drop over the course of the entire photoperiod (CO2 left in the water when the lights go out will off-gas and become "waste"). But, is it really waste if you are maintaining an environment for plants to thrive in?
Greggz, burr740, ChuckM and 2 others like this.

"No Ice? Just Freeze Some Water"
My Dirted 10 Gallon High Tech:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Quagulator is offline  
post #10 of 40 (permalink) Old 04-17-2020, 03:09 PM
Planted Tank Obsessed
 
pauld738's Avatar
 
PTrader: (0/0%)
Join Date: Jan 2019
Location: Modesto
Posts: 315
I know a few on this thread have seen me post this link before but it may be worth a read if your interested.
https://barrreport.com/threads/kh-and-co2-levels.2934/

Among the many things that they talk about, one is the starting point of co2 concentration with that 1.0ph drop and how it affects the end result and another is that some are very negative on using ph as a means to measure absolute co2 concentrations in an aquarium.

I know that that hasn't stopped me from using ph as a guage for co2 concentrations. I'm comfortable with the assumptions that need to be made in order to figure out what my co2 is doing. I think that could be said for most ways to measure, well, most anything in our tanks.
Greggz, ChuckM and Asteroid like this.
pauld738 is offline  
post #11 of 40 (permalink) Old 04-17-2020, 03:13 PM Thread Starter
Algae Grower
 
PTrader: (0/0%)
Join Date: Jan 2018
Location: Upstate NY
Posts: 64
Quote:
Originally Posted by Quagulator View Post
A drop in pH of 1.0 roughly = 30-40ppm of dissolved CO2.
Sorry, respectfully, but this just is not true and I've seen it repeated over and over again. Dissolved CO2 does not change on a linear scale and just checking the previous chart shows that (I haven't seen the raw data questioned for the chart, just the external influences). The chart s based on the Henderson-Hasselbalch equation. I won't pretend to understand it all but what I do know is the change in CO2 ppm is logarithmic, a curve. So the change from a pH of 5.8 to 6.8 is far greater than the change from 6.7 to 7.7

Quote:
Originally Posted by Quagulator View Post
Want zero waste? Install a reactor that achieves 100% dissolution.
Very true, but before I completely understood kit I sprung for a very nice CO2Art Bazooka-type diffuser which now sits under the output of an AC110 HOB. But a reactor is in my future.

Quote:
Originally Posted by Quagulator View Post
Want thriving plants? Accept some waste is needed to achieve a consistent drop over the course of the entire photoperiod (CO2 left in the water when the lights go out will off-gas and become "waste"). But, is it really waste if you are maintaining an environment for plants to thrive in?
It is when it increases the trips I need to make to get the cylinder refilled at US$30/20lbs.
ChuckM is offline  
post #12 of 40 (permalink) Old 04-17-2020, 03:14 PM
Planted Tanker
 
burr740's Avatar
 
PTrader: (132/100%)
Join Date: Feb 2014
Location: Bama
Posts: 5,889
Degas tank water by letting sit in a bowl for about 24 hours. Compare that PH to the PH of the tank with co2 running. A 1 point drop is approximately 30 ppm. That is the most reliable way outside of an expensive test. Forget the KH/PH charts, as already mentioned too many variables affect the KH.

But really what good is knowing whether you have 29 or 36? What can you do with that number that cant be done with the PH drop? If a 1 point drop is too much for the fish, try .8 or .9. If a 1 point drop isnt enough for plants (you'll just have to watch them for a few days) try 1.1 or 1.2 etc.

You'd be doing the same thing if you knew the exact ppm, 31 ppm too much, go down to 27. 31 ppm not enough, go up to 35-40

I understand wanting to know specifically but that knowledge, in my opinion, is no more useful than using the relative PH drop. All you are getting from either one is a reference point from which to raise or lower according to what is needed. And to know what is needed for your particular set up you will have to watch the livestock and also the plants regardless of which metric you go by
Greggz, Quagulator, ChuckM and 2 others like this.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.




burr740 is online now  
post #13 of 40 (permalink) Old 04-17-2020, 03:19 PM
Planted Tank Obsessed
 
pauld738's Avatar
 
PTrader: (0/0%)
Join Date: Jan 2019
Location: Modesto
Posts: 315
Quote:
Originally Posted by ChuckM View Post
Sorry, respectfully, but this just is not true and I've seen it repeated over and over again. Dissolved CO2 does not change on a linear scale and just checking the previous chart shows that (I haven't seen the raw data questioned for the chart, just the external influences). The chart s based on the Henderson-Hasselbalch equation. I won't pretend to understand it all but what I do know is the change in CO2 ppm is logarithmic, a curve. So the change from a pH of 5.8 to 6.8 is far greater than the change from 6.7 to 7.7
Often times what you see on paper, or in an equations, doesn't relate to what is going on in the aquarium. Too many assumptions have to be made.

See my link for how they discuss this very issue. The conclusion was that co2 concentrations are not going to differ at any measurable amount for the water parameters that we usually see in an aquarium.
Greggz, Quagulator and ChuckM like this.
pauld738 is offline  
post #14 of 40 (permalink) Old 04-17-2020, 03:21 PM
Planted Tank Guru
 
Quagulator's Avatar
 
PTrader: (0/0%)
Join Date: May 2015
Location: Forest City ON, Canada
Posts: 2,309
Quote:
Originally Posted by ChuckM View Post
Sorry, respectfully, but this just is not true and I've seen it repeated over and over again.
Could you point me in the direction of these experiments? I myself would like to better understand this for future use. Many times we see these tests / experiment being perform in a completely different scenario than aquariums, and little can be brought over to our world of fish tanks without massive assumptions.


Quote:
Originally Posted by ChuckM View Post
Dissolved CO2 does not change on a linear scale and just checking the previous chart shows that (I haven't seen the raw data questioned for the chart, just the external influences). The chart s based on the Henderson-Hasselbalch equation. I won't pretend to understand it all but what I do know is the change in CO2 ppm is logarithmic, a curve. So the change from a pH of 5.8 to 6.8 is far greater than the change from 6.7 to 7.7
Again, could you elaborate on this a little more? Every tank here that uses pH drop is getting 30-40ppm at a drop of 1.0 - 1.4. Of course it's not the same on every tank that's why I stated:

Quote:
Originally Posted by Quagulator View Post
Start at a 1.0 drop and fine tune it slightly higher to your tank's needs.

Quote:
Originally Posted by ChuckM View Post
Very true, but before I completely understood kit I sprung for a very nice CO2Art Bazooka-type diffuser which now sits under the output of an AC110 HOB. But a reactor is in my future.
Well, I guess some waste is necessary, unfortunately.
Greggz likes this.

"No Ice? Just Freeze Some Water"
My Dirted 10 Gallon High Tech:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Quagulator is offline  
post #15 of 40 (permalink) Old 04-17-2020, 03:34 PM
Planted Tank Guru
 
PTrader: (0/0%)
Join Date: Jul 2018
Posts: 2,196
At the end of the day we really don't know the "exact" levels of many things in our tanks. It's just not feasible, not really necessary beyond just wanted to know. Many levels consistently change anyway and each system is different, so you really just need to use benchmarks and fine-tune from there for your tank based mostly on observation.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

2 Foot Rimless Tank - Under Construction


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Asteroid is online now  
Reply

Tags
None

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the The Planted Tank Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome