When You Up Co2 What Parametres Change

[cuprajake]

hey guy's im currently trying to check my co2 ppm,

my results were this

ph is 6.8
kh is 50 2.8 deg
gh is 60


now if i put this into chucks calc it gives me 13pmm co2 too low,

i upped the co2 yesterday, what readings will change, or what do i need to change to get it up to around the 30 ppm co2

v confusing lol


jake

 

[sophos9]

Hi, I calculate about 14ppm. Upping the CO2 rate will decrease PH

Give it about 24hrs and test KH and PH again then recalculate you PPM, to confirm the calculation you could run a 24hr PH test

HTH

 

[sophos9]

Heres a link to a site I used to find out about the KH / CO2 relationship...

 

[cuprajake]

thanks guy's i have the site already book marked,

as for the 24hr test is that test water as soon as it comes out, then test the same time again to see what it drops too?

so if i up my co2 will i be ok???

jake

also,

with the tests for ph,gh,kh i still feel they are still a little inaccurate as you still have to decide if it looks the right colour lol.

i have a c02 dropper on order so that will tell me too.

jake

 

[sophos9]

Hi

24hr PH test
Take a measure of water say 22:00 and leave it until 22:00 the next night in an open container
The next night, test the PH of the removed sample then test another sample from your tank

Mine measures:
Sample left out for 24hr PH: 7.6
Tank sample PH: 6.6

A shift of 1PH = 30ppm CO2

Do you use Tetrastrips or something? I believe they are inaccurate as the colors are never definitive so I use the 24hr test for confirmation.

Increase CO2 and watch your fishies for any ill effects...

 

[cuprajake]

no i use the nutrafin dedicated liquid tests but i still belive that there is an eliment of guessing thats all.

jake


i'll do the test tonight.



jake

 

[Dave Spencer]

KH = Carbonate hardness, or CaCO3 content of your water to simplify it a little. The calculation I PMd you was to show that 1 degree of German Carbonate Hardness (1dKH) is equal to 17.8ppm (I have also seen 17.9ppm) of CaCO3. KH is sometimes known as alkalinity and refers to the buffering capacity of your water to resist a pH change. People like me who inject CO2 in to soft water (low dKH) run the risk of a pH crash, although I believe this to be a bit of a myth. The CO2 reacts with the CaCO3 in the water to produce Carbonic Acid, which lowers the pH.

All you really need to worry about is that you should aim for 30ppm CO2 and get the lemonade bottle look from your plants. In fact, seeing as you don`t have any fish in there yet, I would aim higher for now. Your best bet is to get your CO2 dropper working with a 4dKH reference solution for the most viable CO2 measurement around at the moment.

Dave.

 

[sophos9]

Dave what do you consider as low KH?

Thought the below might help, you may have read it already...

Myth: A Low KH results in a larger pH swing when adding CO2.

Many people are under the mistaken impression that a low KH results in large pH swings when adding CO2, while raising the KH will result in smaller pH swings. This is not the case. The KH will move the start and end pH values, but the pH swing will be the same for a given level of CO2. You can see this in the chart below, or using the calculation:
Case 1: Assume a KH of 15 degrees, and a starting CO2 level of 4.5ppm, which would result in a pH of 8.0. If we then add CO2, to increase the CO2 level to 28ppm, that would drop the pH down to 7.2, for a pH shift of .8.

Case 2: Assume a KH of just 1.5 degrees, and a starting CO2 level of 4.5ppm, which would result in a pH of 7.0. If we then add CO2, to increase the CO2 level to 28ppm, that would drop the pH down to 6.2, for a pH shift of .8, the exact same as in case 1.

One possible explanation for this myth is that many copies of this pH chart skip some of the higher pH values, for example, jumping from pH 7.4 to a pH of 8.0. If the reader didn't pay careful attention, they might mis-interpret the size of the pH swing. I specifically made sure to include all pH values, between 6 and 8, in steps of .2.

This relationship will break down at extremely low KH levels (below 1 degree), when there isn't enough carbonate to completely buffer the acids present. In that case, the pH can drop quickly and dramatically. But if the KH is 1 degree or higher, then the size of the pH swing when injecting CO2 will be determined only by the amount of CO2 dissolved in the water.

Taken from Chucks Planted Aquariums page - All rights here

 

[griffgrogg]

sorry to highjack this but Im trying to get the right level of CO2 as well, im also testing with nutrafin. Ive been reading with interest the KH4 and permanent CO2 tank testers. Ive seen some ready made KH4 solution being sold on aquaessentials for use with PH probes.................would this solution do rather than have to mix your own ?

 

[sophos9]

Hi, I bought a permanent CO2 tester - waste of time n cash

Once you know your KH you can measure your CO2 just off your PH or using the 24hr PH test

 

[Underwurlde]

"...Once you know your KH..."

And therein lies the problem as this is easier said than done.

The BIG problem wth measuring CO2 is that of accurately measuring pH and to a much greater degree KH. This is where in-tank permenant CO2 testers come in because the reference liquid used uses a VERY precisely known KH solutution (which if prepared by yourself is NOT dependant on measuring KH when preparing), a pH indicator liquid is then added such that it turns a certain colour at a given level of CO2.

If you have 'upped your CO2' then you should certainly expect to see either pH lower or KH raise:

CO2 (ppm) = 3 x dKH x 10^(7.0- pH)

This is not a reversible formula: Don't think that by fiddling with KH or pH will therefore 'make' CO2 go up - the only place that CO2 will come from is .... CO2.

I'll pitch this one in for completeness: To quote VaughnH of the BarrReport....
The pH of 1.0 reduction method over 24 hrs, using the pH of "degassed" water vs. the water in the tank, only works if you know the resulting ppm of CO2 in the "degassed" water. A 1.0 reduction of pH means there is 10 times as much CO2 in the tank water as in the degassed water. But, a 1.3 reduction means 20 times as much CO2. A BIG difference! And, the ppm of CO2 in degassed water can be between 0.5 and 3.0, depending on how long you wait and other factors unknown to me. So this method may be easy to use, but is far from an accurate one.

Andy

 

[sophos9]

Thats really great info there! I cannot get an accurate test using tetrastrips at all looks 3dg but could easily be 6dg?

The BIG problem wth measuring CO2 is that of accurately measuring pH and to a much greater degree KH. This is where in-tank permenant CO2 testers come in because the reference liquid used uses a VERY precisely known KH solutution (which if prepared by yourself is NOT dependant on measuring KH when preparing), a pH indicator liquid is then added such that it turns a certain colour at a given level of CO2.

My live CO2 tester goes one of three colours with a wide range of interpretation so whilst the reference liquid may be very accurate - the measurement system cannot be?

Thanks for the info

 

[Dave Spencer]

Remember Sophos that the 24 hour pH drop test is affected by colour interpretation, just like the 4dKH reference solution, but the 24 hour test also has the inbuilt inaccuracy of other factors affecting the pH of the tank water.

A 4dKH reference solution removes all the inaccuracies apart from colour interpretation, which makes it the more accurate method of the two.

Dave.

 

[sophos9]

Yep you're right

 

[cuprajake]

i thik mine are all messed up,

i tested with a nutrafin test kit.

the kh is done by adding drops till the colour changes you then count the drops then you multiply it by 10 this gives 40 ppm

the gh is done the same but you multiply the drops by 20 for this i get 60ppm

the ph is 6.0 or below.

the tap water is 7.4

so i have had a serious drop

any ideas

the co2 is now turned off till the morning,

and i have some water out to test the 24hr thing


jake